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40 Cards in this Set
- Front
- Back
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symbosis |
an association of 2 or more different species of organisms (neg or pos) |
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symbiont |
microbe |
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ectosymbiont |
organism located on surface of another organism (usually larger) |
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endosymbiont |
organism located within another organism |
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consortium |
hosts that have more than one associated symbiont |
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Mutualism |
-some benefit to both symbiont and host -often parents cannot live separately -mutualist and host are dependent on each other
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Genomic reduction |
outcome of long term relationship. Symbiont loses unused genetic info (creates smaller genome) |
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bacteria-insect mutualism |
-endosymbiotic microbe provides needed vitamins and amino acids -insect host provides secure habitat and nutrients ex. aphid-Buchnera aphidicola interaction -B. aphidicola has extreme genomic stability (no duplication, translocation, inversion, or horizontal transfer) -some of smallest genomes known -make things for eachother and share |
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Protozoan-bacteria-termite mutualism |
-termite provides food for protozoan -protozoan digests cellulose in wood particles, providing nutrients for termite (acetate) -bacteria provide nitrogenous compounds |
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Cooperation |
-positive but not obligatory symbiotic relationship that benefits both organisms in relationship -the 2 organisms can be separated but may not function as well -ex. relationship between cellulose degrading bacteria and nitrogen fixing bacteria |
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Syntrophism |
-growth of one organism depends on or is improved by growth factors, nutrients, or substrates provided by another organism growing nearby -also called crossfeeding or satellite phenomenon |
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Commensalism |
-only one organism benefits (the commensal) and the host is neither harmed nor helped -often syntripic
-ex. Nitrosomonas oxidize ammonia to nitrate Nitrobacter oxidize nitrate to nitrate
-ex. skin or surface microbes on plants or animals |
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Predation (2 examples) |
-among microbes, involves a predator species that attacks, usually killing its prey
-ex. Bdellovibrio penetrates cell wall, grows outside PM, cell bursts
-ex. Vampirococcus- epibiotic mode of attacking prey -attaches to surface via a specialize cytoplasmic bridge -releases digestive enzymes that release cytoplasmic content |
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Parasitism |
-one organism gains (parasite) and the other is harmed (host) -always some co-existence between host and parasite -successful parasites have evolved to co-exist in equilibrium with their hosts -if balance is upset, host or parasite may die |
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Lichens |
-example of parasitism -association only occurs when organisms are nutritionally deprived -fungal partner provides water, minerals, sheltered environment, and firm substratum for growth -alga or cyanobacterium provides organic carbon and oxygen |
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Ammensalism |
-negative impact of one organism on another based on release of a specific cmpd -examples: -antibiotic production by fungi and bacteria (to release and kill) -production of antibacterial pepetides by insects and mammals (lysozyme) |
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Ammensalism |
-use of antibiotic-producing actinobacteria by ants to control fungal parasites
farming ants cultivate fungus (mutualist or cooperation) and also produce actinomycete that controls the parasite that kills the fungus) -ants also produce phialophora to kill the actinomycete to control "cheaters" |
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Competition |
-occurs when two organisms try to acquire or use the same resource
-competitive exclusions principal: one organism dominates and the other is excluded
-or two organisms share the resource and both survive at lower population levels |
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Soil as a microbial habitat |
-level of microbial diversity in soil exceeds that of any other habitat on earth
-supported by complex physical and chemical environments: -soil particles -pore space (critical for movement of water and gases, optimum environment for microbial growth) -bacteria, archaea, fungi, and protozoa use different strategies to take advantage of the complex physical matrix in soil |
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Soil particle |
-soil archaea on surfaces of soil particle -prokaryotes on surfaces within smaller soil pores -terrestrial filamentous fungi-bridge open areas between soil particles
-plants contain C, in ocean bacteria are algae and cyanobacteria |
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Microorganisms in the soil environment |
-numbers can be very high -only small portion have been cultured -soil populations play roles in biogeochemical cycling and the C, N, S, Fe, and manganese cycles -metagenomics used to help understand the complex ecosystems found in soil environment |
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Soil metagenomics |
-75% are unknown -diverse in organic soils -lowest in extreme environments
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Microbial Loop |
-differs from that operating in photic zone of the open ocean -plants (rather than microbes) account for primary production in terrestrial environments -microbes play role in recycling -also differs because plant or insect released degradative enzymes do not rapidly diffuse away( they diffuse in ocean) |
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Epiphytes |
microbes that live on the surface of plants |
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Endophytes |
microbes that colonize internal plant tissues |
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Phyllosphere |
-aerial surfaces of plant -supports diverse microbial community -can protect from UV -can be pathogenic -Sphingomonas- secretes pigment to protect changes in temp on top of soil, also dryer on top of soil |
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Rhizosphere |
volume of soil around the root influenced by materials released from root |
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Rhizoplane |
surface of root |
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Plant roots receive |
30-60% of the net photosynthesized carbon |
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Roles of microbes in rhizosphere and rhizoplane |
-source of nutrients -synthesis and degradation of organic matter -promotion of plant growth -nitrogen fixation |
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Rhizobia |
collective term for microbial genera able to form nitrogen-fixing nodules with legumes -live freely in soil |
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Nitrogen fixation |
-occurs as a result of a symbiotic relationship between bacteria and plants -N2 to NH4+ (ammonium) -plant responds to presence of rhizobia with an oxidative burst to get rid of it -rhizobia must use antioxidant to overcome this
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Nitrogen fixation- once plants see rhizobia are good... |
1. plant roots secrete Flavonoid to stimulate rhizobial colonization of root surfaces (root hairs)
2. Rhizobia then produce Myc/Nod factors in response to flavonoid and trigger root hair cells to curl, forming nodule -Nod factor does to PM to nucleus to transcription to form a nodule
3. Infection thread- bacteria-filled tube-like structure -allows bacteria to go back into plant |
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Bacteroids |
terminally differentiated nitrogen-fixing form of rhizobia |
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Symbiosome |
results from further growth and differentiation of bacteroids |
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Biotechnology and Nitrogen Fixation |
-introduce nitrogen fixation genes into plants that do not normally form this association -genes that create nodules -did in rice but not a lot of nitrogen produced |
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Agrobacterium tumefaciens |
-alpha-proteobacterium -present in soil -causes crown gall disease (tumor) -genes for plant infection and virulence encoded on Ti(tumor inducing) plasmid |
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Agrobacterium-host interaction |
-host infected through wound
-activation of 2-component signal transduction system (induces plasmid to transfer genes to host DNA, T DNA)
-T DNA transferred from bacterium to plant -T DNA directs host to overproduce phytohormones(growth hormones) that cause tumors -stimulated plants to produce opines, chemicals that attract additional A.tumefaciens cells |
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Agrobacterium Virulence genes |
-21 virulence genes found in 6 separate operons -Vir genes not expressed when A. tumefaciens is living saprophytically (in soil) -induced by presence of plant chemicals under cool, acidic conditions |
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Agrobacterium Virulence genes signaling |
Vir A (sensor kinase) activates Vir G (response regulator)
-beings induction of T DNA genes into plant
-T DNA integrates into plant DNA
Plant phenolics --> Vir A --> Vir G -->Transcription of vir genes --> induced type 4 secretion --> transfers T DNA into plants --> causes growth by sec. of phytohormones OR induces opine molecules to signal to other bacterium |
