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263 Cards in this Set
- Front
- Back
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What is the estimated economic benefit of microbes annualy
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Billions
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What are the values of bacterial and normal cells in the human body
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~100trillion bacterial
~1trillion normal |
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What is Mycorrhiza
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A symbiotic relationship between a fungus and a plant where usually nutrients such as phosphate is fixed
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What was the causative agent of the potato famine
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PHYTOPHTORA INFESTANS
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What conditions are needed for bacteria and archaea to exist
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Water, nutrients, C,N,P,S, and reasonable physiochemical limits such as a reasonable temperture
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Roughly how many phyla of bacteria exist
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35
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Define the properties of culture dependent study
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~1% of the original samples will form colonies on plates
Bacteria have different abilities to form cultures |
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Two examples of organisms which cannot be cultures
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Mycoabcterium leprae
Epulopiscium |
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Define Oligotrophy
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Growth at low nutrient concentrations
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Does a higher or lower surface area to volume ratio favour cells
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Higher ratio as nutrients can more readily cross and access the cytoplasm
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How was the phylogenetic tree described in the 19th centruy
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As 2 clades, animalia and plantae
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What was Ernst Hackels tree of life concept
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That life was divided into three distinctive trees, Plantae, Protista & Animalia
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When was the 5 kingdoms concept devised and what did it recommend
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This was the mid 20th century. Divided life further into Monera, Protista, Animalia, Fungi and Plantae
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What was Woese's proposal and what were the categories
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This was the 3 domains concept in 1990 and had simply Bacteria, Archae & Eukarya
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Give an example of a protein which is derived from a prokaryotic source found in Archaea and Eukaryotes
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HSP70 (heat shock protein 70) comes from mitochondrial DNA and can be found in membranes or electron rich areas
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What are the 5 eukaryotic supergroups suggested in '05
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Plantae, Ophistokonta, Chromalveolate, Rhizaria/Cercozoa and the Excavates
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Since Simpson & Rogers addition, how many Eukaryotic groups are there and how is the tree of life split into two
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There are 5-6 eukaryotic groups and the tree of life is split into UNIKONTS and BIKONTS
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What different clades is the chromalveolate phyla made up of?
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Apicomplexans, Alveolates, Ciliates & Chromistans
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Which group in the chromalveolate group is exclusively parasitic
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Apicomplexans
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What structure is to be found in all Apicomplexans
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The apical complex (within the infective stage)
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Are flagella present in the Apicomplexans and if so in which stage
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Found in some male gametes but is almost completely reduced
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Describe the mitochondria of the Apicomplexans
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The mitochondria have tubular christae
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What is the infective stage of an Apicomplexan called
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Sporozooite
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What is the role of the apical complex and where is it found
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The apical complex is found towards the anterior end of the Sporozooite and is used to infect hosts
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Name two diseases caused by Apicomplexans
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Malaria & Cryptosporidiosis
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Name the two main types of Plasmodium which infect humans and which one is responsible for 80-90% of deaths
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Plasmodium vivax and Plasmodium falciparum. The latter is responsible for high mortality
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What are Alveole
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These are flattened vesicles that lie underneath the cell membrane.
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What kind of environment are Dinoflagellates likely to be found in
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Aquatic, either freshwater or marine
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Describe the difference between Thecate and Athecate Dinoflagellates
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Thecate Dinoflagellates have thecal plates under the plasma membrane whereas Athecate DInoflagellates have external plates
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Roughly how many described species of Ciliates are there
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13,000
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Describe a Macronucleus
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This is polygenomic and transcriptionally active. It controls the cell phenotype. One is produced at the start of each generation and then degraded for mitosis.
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Describe a Micronucleus
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This is usually diploid and transcriptionally inactive. Undergoes mitosis & meiosis and provides continuity between sexual generations
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What is the role of Cilia
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Cilia are short stiffened rods which beat to both feed and provide locomotion
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Describe the difference between Homotrichous and Heterotrichous
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Heterotrichous have longer cilia which are almost used as legs.
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What are Tripartate Mastigonemes
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These are composed of glycoprotein and are produced in the ER cisternae. They are found on Heterokonta
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What are the characteristics of Heterokonta in relation to flagella
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One flagella is smooth and backwards facing whereas the other is forwards facing and covered in two rows of Tripartate Mastigonemes
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What kind of christae do the mitochondria of Heterokonta have
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Tubular
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Name the representatives of the 'first clade' of Heterokonta (the colourless protists)
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Bioecids, Labyrinthulomycetes & Opalinids/Blastocysts
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Describe Bioecids
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Free living bacteriotrophic flagellates common in marine ecosystems
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Describe Labyrintholomycetes
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Exclusively marine colourless protists
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Describe Opalinids
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These are a small group of ciliate like gut commensals or gut parasites
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What are the two main groups of Labyrinthulomycetes
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Thraustochytrids & Labyrinthulids
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Where are the Rhizoid like slime structures of Labyrinthulids connected?
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Sagenogen
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Why are Labyrithulids key in some marine ecosystems
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They decompose fallen matter such as leaves
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What are the members of the Heterokonta 'clade 2'
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Ochrophyta, Hyphocytrids & Oomycetes
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Describe Oomycetes
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these are biflagellate with a fungal like morphology & life-cycle
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Describe Hyphocytrids
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These have a single anterior flagellum and are parasitoids
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Describe Ochrophyta
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These are the golden brown photosynthetic algae. Examples are brown seaweeds
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Which two groups did Tom-Cavalier Smith propose as the 'Pseudofungi'
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Hyphochytrids & Oomycetes
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What were Hyphochytrids originally classified as and how to they gain nutrients
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They were classified as Chytrids but was rejected due to their single anterior flagellum. They gain nutients through phagocytising cytoplasm
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what were Oomycetes orignally studied by and to what group are their Zoospores similar
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Originally studied by mycologists due to their fungal like mycelium, and the zoospore bear similarity to the Ochrophyta
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Give two example of Oomycetes which have an impact on humans and what they cause
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Saprolegniales which is a major cause of disease in salmon, and Peronosporales which caused the potato blight
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On what basis are the Amoebozoans grouped
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They are generally based on molecular characteristics
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Give two characteristics of the Amoebozoans
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Many lack mitochondria and those that do have them are characterised by branching tubular christae. They also have a tendency to make broad pseudopodia which is also known as Lobopodia
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Give an example of a 'testate' amoebae and describe it
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Arcella is an example of this. It has a 'shell' made of fused glycoprotein units and a strong chromidial network to secrete new glycoprotein units
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What is the significance of Amoebozoans and where are they found
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They are usually found in environments with moisture, and they are important bacteriovores
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Describe Entamoeba
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This inhabits the intestinal mucosa of some animals including humans. It is able to migrate around the bloodstream. Only 6 can infect humans and only E.hystolytica causes disease
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What are the characteristics of the 'sensu stricta' clade of ophistokonts
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They have very few single celled members and contain the highest number of species as they include both the fungi & metazoan animals
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Name some features of the Ophistokonta
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They have mitochondria with flattened plate like christae, glycogen is main storage agent and chitin is present in cell walls
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Name the 6 groups of Ophistokonts
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Nucleariids, Fungi, Microsporidians, Ichthyosporids, Choanoflagellates & Animals
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What type of mitchondria do Nucleariids have
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The have discoid mitochondria which is not typical for the Ophistokonts
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Roughly how many described species of Fungi are there and why are they essential
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There are roughly 70,000 described and they are essential to plants such as through mycoorihiza but also pathogens of many things
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Why are fungi vital for most higher organisms
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Because they form intimate relationships with plants such as mycorrhiza but also inhabit environments such as the rumen and digest cellulose
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What are the 5 main groups of Fungi
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Chytrids, Zygomycota, Glomeromycota, Ascomycota & Basidiomycota
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What are the earliest diverging Fungi
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Chytrids
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What are the 3 recognized categories of Chytrids
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Rumen Chytrids, Chytrids (sensu stricta) & Blastocladialian Chytrids
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Describe the zoospores of the Chytrids
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The are posteriorly uniflagellate
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What is the name of the Chytrid which is a lethal parasite of amphibians
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Batrochochytrium
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Describe the hyphae of the Zygomycota
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They are uncompartmentalised and aseptate.
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How do sexual spores arise in Zygomycota and in what are the asexual spores produced in
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The sexual spores arise through two mating hyphae to produce Zygospores, and asexual spores are produced in pin head like sporangia
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Name some saprotrophic plant, human & insect Zygomycota pathogens
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Mucor, Rhizopus & Entomorphthorales
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Describe the Glomeromycota
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They are widespread on the roots of herbaceous plants. Large globose thalli producing thread like hyphae. No known sexual stage and cannot be cultures in labs
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Describe the characteristics of the Ascomycota
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these have hyphae which are compartmentalised by cross walls. They are septate and produce ascospores in sac like 'asci'
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Give two examples of the Ascomycota
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Penicillium and Aspergillus
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Describe the characteristics of the Basidiomycota
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These are the most highly evolved group. Are septate with clamp connections to ensure nucleus distribution. Spores produce pistol like basidia which bear basidiospores
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Give the characteristics of the Microsporidians
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Sister clade to fungi, obligate intracellular parasites, common in insects + fish. ~1200 described species. Pathogens of silkworms + bees & control agents against locusts. Role in humans rising due to immunocompromisation
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Why are the Microsporidians energy parasites
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They lack mitochondria so have to tap into cells for ATP. Can manipulate cytoskeleton to move mitochondria closer to microsporidian.
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What kind of cells can Microsporidians produce and what is their purpose
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They are able to produce syncytial cells which can fuse together to form much larger entities
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What do microsporidians exist as outside the host
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Spores
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How large are microsporidian spores
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1-50 micrometers
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What is the composition and layout of a microsporidian spore
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The exospore is made from protein, endospore from chitin. One or two nuclei to be found at the apex
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What are the alternative names for the Ichthyosporids
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Mesomyceozoans or DRIPS
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How many Ichthyosporids have been cultured or described
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About 70-100 described, only 8 cultured
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What is ichthyosporids association with other organisms
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They are either commensals or parasites always found in association with animals
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Name the member of the Ichthyosporids responsible for disease outbreaks in herrings and salmon
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Ichthyophonus which has a complicated life cycle that varies with pH
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What reproductive structures do the Ichthyosporids release and are they host specific
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The structures released are spores or amoebae and they are not host specific
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Describe the Choanoflagellates
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There are about 120 species mainly marine. Common in plankton, many sessile representatives.
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What is the closest related organism to choanoflagellates and why
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Sponges due to similarity in cells of Choanocytes
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Describe the Myxozoans
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Parasites of fish, secondary unicellular animals from cnidarian ancestors
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Why can't we classify organisms on the basis of morphology
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May organisms look identical so isn't a way of discriminating between species
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Why is using an organisms source of energy also a poor way to classify organisms
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Using this method would still only bring us down to about 6 groupings of organisms which is far too few
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Describe the 'Biological species concept'
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The biological species concept is "groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups"
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Why does the biological species concept not hold true and give an example
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Although organisms may be of the same species, they may not necessarily be able to breed due to things such as size limitations. Think about a pug mother harboring German Sheppard young
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What is the value for DNA-DNA hybridisation similarity to be accepted as of the same species
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>70%
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What value are 16sRNA similarties unlikely to have >70% DNA-DNA hybridsation similarities under
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97%
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Roughly what percentage of bacteria can be cultured in laboratory conditions, and why is 16sRNA sequencing so key
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0.01% roughly can be cultured, so using 16sRNA can give us an idea of where the organism lies on a phylogenetic tree
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How many genes are in the human genome and how many are in the microbiota?
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30,000 human genes, 3,000,000 microbiotal genes
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Define the 'human microbiota'
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The human microbiota is the total community of microbes associated with the body
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In which ways are microbes able to cause disease
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This can either be through pathogenic bacteria that aren't part of the microbiota being introduced or a change in conditions that disrupts the normal microbiotal populations
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What functions are microbes in the body involved with
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They are involved with digestion in addition to vitamin production
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How does the microbiota aid the human body
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The microbes can resist pathogens, occupy niches to prevent invasion & educate the immune system
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How many 16sRNA sequences were retreived from a microbiota study
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1,070,000
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How many phyla of organisms were found in the study
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22
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What is the largest reservoir of bacteria
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The gut
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Roughly how many cells are there in every g of gut lumen
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10^12
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What is the relationship between the gut microbiota of similar animals
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The microbiota is very similar between similar organisms
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Which type of mammal has the most gut microbiota diversity and which has the least
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The herbivores have most and carnivores the least
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In a 2005 study, how many species were found in the gut
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11,831
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What type of bacteria do obese mice have more of, and which do lean mice have more of
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Obese have more Firmicutes and lean mice have more bacteriodetes
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What did bomb caliometry prove about mouse gut microbiota
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The obese microbiota are able to extract more energy from food which results in there being less energy in faeces
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What are all the genes collectively in the microbiota known as
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The microbiome
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What is the concept of microbial guilds
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The idea of microbial guilds is that there groups of organisms which fufill the same microbial niches even if they are different species
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How do SRB (sulphur reducing bacteria) produce H2S
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Through the use of hydrogen from other fermentation - produces bad odour
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What is the source of sulphur for these organisms
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Sulphur from carbonates drinks and other drinks naturally high in sulphur are a source
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Whats the term used for disbalance in the human microbiota
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Dysbiosis
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Give an example of bacteria that produce antimicrobial compounds which inhibit the growth of dangerous organisms
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Bfidiobacteria
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How can faecal transplants restore normal microbial populations
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They can add bacteria which are not at their normal levels. Paticularly effective against clostridium difficile
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What is the role of prebiotics
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The role of prebiotics is to increase already present bacterial populations rather then to add new ones
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What condition has Mycobacterium Vaccae been linked with
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It has been linked with serotonin production so lack of interaction has been linked with depression
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An organism with an optimum pH of 3 or below
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Acidophile
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Organism with optimum growth pH of 9 or above
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Alkaliphile
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Organism that can live within rocks
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Endolith
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Requires at 0.2M of NaCl for growth
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Halophile
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Lives in rocks in cold deserts
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Hypolith
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Tolerates high levels of heavy metal such as cadmium
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Metalotolerant
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Can grow in nutritionally limited environments
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Oligotroph
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Grows at optimally high hydrostatic pressure
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Piezophile
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Thrives at temperatures under 15 degrees
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Psychrophile
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Resistant to high levels of ioninsing radiation
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Radioresistant
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Can survive at temperatures between 60-80 degrees
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Thermophile
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Requires little water to survive
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Xerotolerant
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What are hyperthermophiles
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These thrive in hot environments and have optimums of 80 degrees. Discovered in '69 by Thomas Brock in yellowstone
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What are the characteristics of 'strain 121'
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Can tolerate 121 degrees and is bacteriostatic up to 130. When transformed to cooler medium continues to grow. Metabolises by reducing iron
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How are hyperthermophile membranes adapted
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Contain membrane spanning tetra-ether lipids that give high rigidity. Some contain terepenoid like lipids so the membrane composistion changes at different temps
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Describe the nucleic acid composistion of hyperthermophiles
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They have high G+C which gives the DNA a higher denaturation temperature. They contain DNA binding proteins such as histones similar to the eukaryotes
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Describe the proteins and solutes of the hyperthermophiles
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They have lots of chaperonins, up to even 80% of all proteins. The enzymes have a higher number of H bonds and salt bridges. Protein stability is increased by presence of solutes such as K & cDPG
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Describe the characteristics of Physchrophiles
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Can grow below 15 degrees, not thermoregulated
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What temperature can Psychrobacter cyropegella grow at
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-20
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How do psychrophiles survive cold conditions
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They have protein rich helices and polar groups to allow flexibility, have antifreeze proteins, more fluid membranes as many cis-fatty acids & have active transport
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Describe the characteristics of Oligotrophs
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They tolerate very low carbon concentrations of about 1ppm. Have slow growth, low metabolic rates & population densities
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Describe halophiles
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Need 10-15% salt, mainly aerobic, specialised cell walls, pigmentation in form of Bacteriorhodopsin for photosynthesis
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What gives the red pigment of halophiles and what caused the red sea
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Carotenoid pigmentation gives the pinkish colour, and Halobacterium spp. caused the sea to go red
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How do halophiles survive high salt
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Enzymes optomised to high salt
Proteins smaller so act strongly w. water Import K or Cl solutes to maintain osmotic pressure |
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What causes desert varnish
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Xerophiles create desert varnish as they can survive low water. The varnish itself is caused by Mn & Fe
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Give examples of the conditions that Deinococcus radiodurans can tolerate
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This can withstand cold, dehydration, extreme radiation (4million rads), genotoxic chemicals, oxidative damage, vacuum, low pH
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How does Deinococcus radiodurans deal with cell repairs
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Contains many DNA repair enzymes such as RecA (matches shattered DNA & splices back together). In repairs, cell building activities shut down to keep DNA in place. High Mn(II) prtects from oxidative radiation
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Give some uses of Deinococcus radiodurans
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Has been genetically modified to consume & digest solvents in addition to removing heavy metals from the environment. Detoxifies mercury & toluine produced in radioactive weapons manufacture & used to store information
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Which phyla of archaea live in hot sulphur rich acidic springs
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Crenarchaeota
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What characteristics do bacteria towards the base of the tree of life have
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They tend to be hyperthermic extermophiles, examples are Aquifex and Thermotoga
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Name the evidence for extremophiles being the earliest organisms
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They have H2 metabolism which is what would have been the abundant respiration method in the early earth
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How much have hyperthermophiles evolved from their ancestors
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Not very much, result of extreme habitats with little competition. Halophiles appear to have undergone quicker evolution as aren't in specialised habitats
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What is isolated from Thermus aquaticus
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Taq polymerase
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What is isolated from Sulfolobus solfataricus
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Alcohol dehydrogenase to catalyse the conversion of alcohols
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What can bacteriorhodopsin be used for
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Bacteriorhodopsin can be used to generate elctricity from light, as halobacterium use this as a source of energy
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What does SLiME's stand for
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Subsurface lithoautotrophic microbial ecosystems
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How do SLiMEs survive
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They survive through using carbon from CO2 and using iron and sulphur to provide energy. They are able to persist indefinitely as there is no input from the sun
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What is the bioflux of H, C, N, O & S driven by
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These are driven by redox reactions
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What energy sources do chemolithotrophic bacteria require
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These bacteria require H2S, H, & NH3 provided by the geochemical process
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How can CO2 be fixed anaerobically
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This can be fixed through methanogens. undergo reactions CO2+4H2 --> CH4 + 2 H2O
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Where do plants and animals get sulphur from
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They gain sulphur from sulphate & amino acids
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What do microbes use sulphur as
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Sulphur is used by microbes as an electron donor in anaerobic photosynthesis, and as an acceptor in aerobic respiration
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What is Mycelia
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Mycelia are apically extending systems of tubes which secrete enzymes for nutrition - known as osmotrophic nutrition
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What type of organism creates 'fairy rings' and how
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Marasimius oreades creates colonies. It breaks down matter as it grows and releases nitrogen which stimulates growth. The hyphae aggregate to cords strands and rhizomorphs
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What kind of fungus can stretch tree to tree
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The honey fungus
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What are the properties of Saprotrophs
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These colonise and breakdown leaf litter and woody substrates such as fallen tree trunks & twigs
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Where are saprotrophs usually found on open pasture and what are they doing
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They are colonising and breaking down animal dung & recycling nutrients.
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What's a standard saprotrophic succession
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Standard succession includes Zygomycetes (sugar moulds) --> Ascomycota (cup fungi) --> Basidiomycota (toadstools). Comes as a result of using increasingly complicated substrates
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Give characteristics of saprotrophic litter fungi
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These fungi breakdown dead plant matter such as needles. The size of the fruit body is related to the food resource.
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Give examples of saprotrophic fungi
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Agaricus, Collybia & Clitocybe. Collybia confluens rapidly bleaches leaves as lignin and cellulose removed. Collybia butyraceae coloniese spruce needles
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How have organisms evolved to deal with the digestion of wood
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Bacteria & fungi have evolved enxymes to deal with it, and insects have co-evolved to have these organisms in their gut to help digest
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What's the difference between heartwood and sapwood
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Sapwood is the outer layers and has living parenchyma which is packed with sugars. Heartwood is dead and full of resistant phenolics which are naturally durable. Heartwood to sapwood ratio increases with age
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What organisms are capable of breaking down lignified wood
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Manily basidiomycoata are capable of this & can breakdown lignin which is difficult as its a complex polyphenolic
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Give the qualities and an example of blue stain fungi
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Blue stain fungi such as Trichoderma can invade parenchyma and move into vessels. Can penetrate wood walls but dont affect strength. Reduces commercial value
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Give the qualities of soft rot fungi and examples
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Discovered in rotting power lines in australia. Produce diamond shaped cavities in S2 layer of wood
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Give the qualities and examples of brown rot fungi
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These are mainly basidiomycetes. Remove hemi-celluloses and celluloses but cannot degrade lignin. Results in wood cracking. Includes beefsteak fungus (Fistulina hepatica)
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Give the qualities and examples of white rot fungi
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These are basidiomycete fungi and remove all constituents of wood. Bleach wood white and enabled zones to be seen known as spelted wood. Ganoderma, Stereum and Trametes vesicolor are examples
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What do black melanised zones in wood represent
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Black melanised zones represent the boundary between one genotype and another.
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Where does the substrate for agious bisporous come from
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This comes from other primary industries such as wheat straw, poultry manure and stable waste. Could pose environmental threat if not recycled
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Describe the first phase of Agaricus bisporous production
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COmposting is carried out through manure and wheat straw for example. Chicken manure is added in a controlled manner and heaps are turned daily for ~304 days
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Descrbe the second phase of Agaricus bisporous production
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The compost is pasteurised, put in controlled chambers. Temps climb to 60 degrees to kill unwanted insects & organisms.
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Describe conditioning in Agaricus bisporous production
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Compost is maintained between 48-52 degrees allowing gaseous ammonia to be converted to microbial biomass. When ammonia is below 10ppm, cooled to below 25 degrees
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Describe phase 3 of Agaricus bisporous production
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In this spawning takes place. Wheat grain with mycelium added to compost. Temp of compost climbs to 25 to allow CO2 to build. For next 10-14 days humidity of 95-100% maintained to prevent drying out
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Describe phase 4 of Agaricus bisporous production (casing)
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After spawning, casing layer of peat/limestone added 5cm thick. Provides humid microclimate for fruit body formation. Fungus is allowed to colonise casing layer with water added as required. Once infested, moved to fresh air to induce fruit body formation
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Describe phase 4 of Agaricus bisporous production (cropping)
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Pins develop into mushrooms which grow in flushes. AFter 17-21 days first harvest. Most growers harvest 3-4 flushes a crop. Temps held between 16-19 degrees. Average yield of 22kg/m from 95-100kg of compost
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Name the three growing systems for Agaricus bisporous
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Tray growing, Bag growing and Shelf growing
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What are the three grades that mushrooms are sold in
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Buttons: unopened mushrooms which attarct highest returns
Cups: buttons which have grown until cap has begun to open Flats: Cups which have expanded so all gill seen Factory: Mushrooms of all stages, not up to fresh market standard |
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Desribve the Shiitake mushroom production process (Lentinus edodes)
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Grown on logs, pine, beech. Logs soaked and partially dried to 35-40%. Agar cultures added to plugs 2.5cm deep. Sealed with wax & moisture content maintained. Logs stored under 60-70% shade. Fruiting induced by cooler temps. Flushes last 6-12 weeks
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What is the difference bewteen Lentic and Lotic watersystems
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Lentic means flowing wheras Lotic means still
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What organisms are key saprotrophs in flowing freshwater and what is their genus
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Aquatic Hyphomycetes are key saprotrophs - have tetradiate spores. Imperfect stage of ascomycote genera Hymenoscyphus
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What are the 'water moulds' and what are their characteristics
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They are Sapeolegniales and can be isolated from lotic and lentic. Some can tolerate esturine & marine conditions. Non-specialised saprotrophs, cause problems for crutacea and fish
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Describe the issues with aquaculture and saprolegnia parasitica
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Generally fish problem but has spread to cave newts in Slovenia. Aquaculture causes problems as there is stick genetic uniformity, stress, physical damage & degradation of immediate environment
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Describe obligate marine parasites and give an example
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Able to live & reproduce in marine environments. Facultative marine parasites exist such as Scopulariopsis.
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Why can much fungi cultured from seawater not be considered true
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Spores may germinate but actually be from external sources
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Give some traits of marine fungi, in paticular Nia vibrissa
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Most have inconspicuous fruiting bodies, largest do not exceed 3mm, Nia vibrissa is 4mm. Coastal over oceanic, colonise seaweed & sandgrains
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Describe marine yeasts
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Planktonic and can survive Euryhaline conditions
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Give example of organisms and how they cope with the marine environment
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Dendryphilla concentrate sodium within the cell vacuole. Polyols such as glycerol accumulate in the cytoplasm to balance solute potential. Thraustochytrium utilises proline and glutamine to serve the same role
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Name one of the most distinctive features of marine ascomycetes
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One of the distinctive features is the ascospores which come in alaborate shapes. Serve to facilitate transport an aid adhesion to substrates
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Give examples of fungi genera on marine timbers
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Lulworthia, Dendryphiella, Humicola & Zelerion - usually affect woods such as beechwood and pine
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Explain how Cellulomonas is associated with Teredo navalis
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Teredo navalis is an important wood borer, however it requires Cellulomonas. The larvae of cellulomonas settle preferably on fungal infested wood
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What is one of the deepest growing fungi and at what depth is it found
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Peronica abyssa is the deepest at 5000 metres down
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What organisms are said to be holocarpic and what does this mean
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Marine chytrids are said to be so which means that spores develop into an entire thallus
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What are the most basic marine fungi and what are their properties
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The holocarpic Oomycetes are the most basic, appear to bed both parasitic and asexual
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Which fungus infests blue crab
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Lagenidium callinectes
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Describe the properties of Eurychamisa
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Parasite of brown alage, simple holocarpic thalli. Cysts form characteristic peripheral nets within the sporangium. No known sexual stage but shares characteristics with haptoglossa
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Give the traits of Halophytophtora vesicula
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Rapid coloniser of mangrove leaves. Colonisation inhibited if large bacterial films on leaves. About 10 species describe and effect Arbutus and Prunus
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Describe how a symbiotic relationship with fungi is started
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Involves synthesis of inhibitory compounds such as phytoalexins and localised cell death- - hypersensitivity
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What molecules help suppress the hosts immune response
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Effectors
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What are the two types of mycorrhizal associations and what are the differences
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Ectomycorrhizal - Form dense sheath around roots and form hartig net
Endomycorrhizal - penetrate into root tissues and form invasive arbuscules inside cortical cells |
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What does VA stand for in VA Mycorrhiza
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Vesicular Arbuscular, theya re the most common group of mycorrhizae
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What group do the VA mycorrhiza come under
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They come under their own group called the Glomeromycota and have the longest fossil history of any fungi. Mainly associated with grasses
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Give characteristics of mycorrhizae
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Mainly associated with roots of trees and shrubs. Fungus scavenges nitrogen and phophorous
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How do ectomycorrhiza establish themselves
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Generally easier to work with than VA counterparts. Many genomes such as Laccaria bicolour have been sequenced
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Describe the role of MiSSP7
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Secreted by Laccaria bicolour, enters root cells and targets nucleus. Alters the transcriptome to suppress immune response
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What's the role of cyanobacteria in lichens
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These bacteria satisfy the carbon requirements of the fungus. Gain in return niche to live
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What are the three layers of a lichen and what are their roles
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Cortex: outermost layer of thallus composed of compacted fungal cells
Medulla: elongated central cells containing mycobiont Photobiont layer: thin zone immediately beneath cortex where photobionts concentrated |
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Give some traits and examples of the photobionts
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Belong to chlorophyta, trebouxia & coccomyxa being common. Claudonia is always associated with Trebouxia, and often Peltigera with Coccomyxa are primary photobionts
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Give some trauts of the Mycobionts involved
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Mainly belong to the Ascomycota, half of which are believed to be lichenised. Both Apotheciate and Peritheciate species involved. Some associated with basidiomycetes such as Omphalina
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What is meant by polyphyletic and how can it be applied to lichens
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Many lichens may have this state which means it has arisen and been lost more than once in evolutionary history
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Define Endophytes
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Fungi that live as commensals within host tissue, when the relationship becomes uneven it turns to parisitism
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Define Necrotrophs
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These feed on dead or dying tissues, often secrete enzymes to break down tissue
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What's the difference between Facultative and Obligate biotrophs
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Facultative biotrophs are able to infect and feed off dead as well as living cells whereas obligate can only live on live organisms.
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Where do pathogens usually excrete effector molecules from
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The Haustoria or Intercellular hyphae. Can be expressed in apoplast or cells themselves
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What's the general route of infection for necrotrophs
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General route of infection for these is through wounds
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Give two examples of necrotrophic fungi
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Penecillium expansum causes soft rot. Ventura Inaequalis causes the apple scab disease
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What is the alternative name fir Facultative biotrophs and when do they switch to necrotrophy
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They can also be known as hemibiotrophs and are capable of infecting living as well as dead cells. Switch to necotrophy late in infection
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Give an example of a hemibiotroph that acts on seedlings
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Phythium spp.
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What is the cause of dutch elm disease and what does it do
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Dutch elm disease is cause by Ophiostoma Ulmi. The insect vectors are Scolytus spp., pathogen spreads in vascular system/
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Describe the properties and function of Haustoria
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Almost 'drinking' structures. Penetrate cells, sealed by neck band region to prevent solute leakage. Host membrane is not penetrated, invaginates around it. Extrahaustorial membrane is specialised
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Describe powdery mildew and the rice blast fungus
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Powedery mildew is caused by Appressoria & the rice blast fungus is through Magnaporthe grisea. They form an apressorium which develops high osmotic pressures.
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How old have mycorrhizal associations been proven to be
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Evidence has shown them in fossils up to 450 million years old
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Where are ecotomycorrhiza common
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They are commonlu found in woodland with fruiting bodies on sept-oct. Can form deep networks and even link plants together
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Up to what percentage of nutrients can hyphae contribute to a plant
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Can contribute up to 80% P, 25% N & 10% K to the plant.
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What is the mantle of the mycorrhiza
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This is a thick network of hyphae which is external to the roots.
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Give some examples of ectomycorrhizal organisms of value
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Hedgehog fungus, truffles and death cap are all examples of ectomycorrhizal assosiations
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How many species are there of endomycorrhiza
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~150-200
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What do ericoid mycorrhiza have associations with
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They have associations with shrubs such as Rhododendron.
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What are arbiscules
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These are produced by arbiscular mycorrhiza and create a tree like structure within a plant which is the site of nutrient exchange
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What different approaches can be used with mycorrhiza in terms of bioremediation
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They can help plants stabilise themselves in order to get rid of contaminants or the fungus itself may even have the ability to help better the soil
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What were the findings in relation to poplar trees and diesel with and without mycorrhiza
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Initially, removal is greater, likely as the plant establishes itself quicker, however after this, overall diesel is removed less from the soil, probably as an interaction between fungus and soil organisms meaning that these factors have to be taken into account
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What does rose bengal select for and what compounds are in it
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Selects for fungus, contains Chloramphenicol which is an antibacterial agent
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What does starch casein select for and what compounds are in it
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Contains Cycloheximide & Nystatin which are antifungal compounds. Agar selects for actinomycetes
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How can food be spoilt and what defines spoilt food
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When it's lost its acceptable qualities such as taste or smell. Can occur through physical such as dehydration, chemical such as oxidation or infestation such as insects.
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How many cells are associated with spoilage
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10^8 to 10^10 cells/ g-ml-whatever are associated with food spoilage
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What toxin does Penecillium expansum produce in apples
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It produces Patulin which is a mycotoxin, EU limit is 50ug/kg in fruit juices
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Give examples of organisms adapted to spoilage in things such orange juice
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P.citrinium & P.digitatum are adapted to the low pH's of orange
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What organism can spoil jams due to its high tolerance of low Aw's
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Eurotium, can grow as low as Aw 0.6. Exrophile and produces heat resistant spores
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Give the properties of Alicyclobacillus and why it causes problems
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It can grow at low pH's of 2-4 & produces heat resistant spores. Causes an off taste through Guaiacol. Storage under 12 degrees can help
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Name the different washing techniques that can be used to help reduce food contamination
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Washing, high pressure washing to remove rotten parts or washing with chlorine to reduce the microbial load
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How can Lemons be preserved
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Lemons can help be preserved with the addition of waxing and pesticides
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Name a broad spectrum bacterioside and what it's effective against
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Nisin is broad spectrum and paticularly effects gram positive organisms.
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Name the chemical agent that's used a sprout supressant in potatoes
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CIPC
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Describe the attachment phase of biofilm production
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Free living cells attach using flagella or pilla. Move through twitching and eventually microcolony formed. After critical mass, certain genes expressed to cause irreversible attachment. Flagella & pilli needed for microcolony formation
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Describe the exopolysaccharide phase of biofilm production
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Through quorum sensing cells bind firmly to the surface & produce EPS (extracellular polymetric substance). Glycoproteins & PS's produced to cement biofilm. Contains things like enzymes and nucleic acids
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Describe the maturation phase of biofilm production
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In this the cells grow into complex 3D structures. Adopt physiological properties different to planktonic such as downregulation of flagellin. Channels exist between groups in the biofilm
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What are the different mechanisms of biofilm dispersion
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Can be through abrasion, enzymic dispersion or human intervention. Active methods include Dispersin B & Alginate lysase
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Explain the method of action of Dispersin B
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It's a glycoside hydrolase produced by Periodontopathogen A. Mutants of this can form biofilms but cannot disperse them
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Explain the method of action for NucB
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This is an extracellular DNAse from Bacillus licheniformis. Capable of breaking up gram negative and gram positive biofilms.
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How is heterogenity in biofilms formed
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This is through the different environments within the biofilm. Will be different levels of nutrients as well as toxins
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How much more resistant to sanitisers are biofilms
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they can be up to 500x more resistant. Some drugs actually stimulate the biofilm to lay down more extracellular matrix
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What percentage of bacterial infections are associated with biofilms
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Up to 80%, can form in the lungs of cystic fibrosis patients and on contact lenses, heart valves and catheters.
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Give an example of a biofilm that can cause health damage in air conditioning units
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Legionella penumophilla can cause problems in air conditoning units and can can legionellas disease
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What solutions are being devised to deal with biofilms
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Surfacants such as sufactin have been developed to prevent Salmonella enterica from growing in urethral canals. Nanoparticles lead to research, Cu &Ag are used. Current research is on blocking signals that lead to matrix formation.
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Give an example of a beneficial biofilm
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In cows they digest cellulose and synthesize amino acids and vitamins such as B & K12
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