Bacteria And Viruses

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3 distinct shapes of bacteria

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Bacillli = usually single Rod shaped
Cocci = spherical shaped
Spirilla = spiral shaped

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Cocci

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- spherical shaped
found as
- Diploids = pairs of spherical shaped bacteria
-Chains of spherical shaped bacteria

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Endospores

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constructed of a central core of DNA that is surrounded by an impenetrable layer
- can remain viable for millions of years and are capable of causing serious diseases

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Bacci

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-some have adapted to survival during unfavourable conditoins by forming dormant/resting cells called endospores which are resistant to severe physical and chemical stresses

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Spirilla

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-actually made from rod shaped bacteria

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Bacterial Cell structure (internal)

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-surrounded by cell membrane
-which acts as barrier and holds proteins and other parts of the cytoplasm in place
-Allows for transport of energy and materials across it via a concentration gradient
- single ring of genetic material (chromosome) encased in a nuceloid

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Cell wall

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-composed of peptidoglycan (not cellulose)
2types:
-->gram positive and gram negative

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Gram positive

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thick cell wall

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gram negative

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thin cell wall (most bacteria fall into this category)

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Flagella

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-used for motility by rotating and driven by energy at the base
-can be found alone at each end, in clusters at the poles or all over the cell

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Pili (pilus = singular)

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used for transferring genetic material between cells

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Fimbriae

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-fine filaments of protein that aid in the attachment to other cells

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Bacteria gliding

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-way of movement
-exact mechanism by which this happens is currently unknown although there are theories that include ejection of slime and movement of pili

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Twitching motility

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-way of movement
-special pili are used as a hook that is extended repeatedly and used to pull the bacterium along

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obligate aerobes

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must have oxygen to survive
-ex. Eubacteria

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obligate anaerobe

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can only grow in absence of oxygen
-ex. Archaebacteria

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Facultative anaerobes

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prefer environments with oxygen but can live in places without it

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Glycocalyx

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-layer outside cell wall
-gelatinous layer
-if layer is firmly attached to the wall it is called a capsule
-if loosly attached, its called a slime layer
-used to protect bacteria from host's immune system attack

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Autrophs

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-organisms that make their own food
--> Photosyntheitc = use light for energy
--> chemosynthetic = use of chemical substances for energy

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Heterotrophs

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-organisms that obtain food from other sources
-->Saprophytic = obtain raw materials form dead and decomposing matter
-->Parasitic
-->Symbiotic/mutalistic(bacteria in human colon

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Chemotrophs

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-perform fermentation for food

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transmission

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direct contact
airborne droplets
bacterial toxins in food (ingestion)
fecal contamination in food
water
vector bites (mosquitos)

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Binary Fission

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-type of asexual reproduction
-organism replicates DNA and divides in half, producing 2 identical daughter cells
-does not involve exchange or recombination of genetic info

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Conjugation

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-type of sexual reproduction
-paramecia and some prokaryotes exchange genetic info
-hollow bridge forms between 2 bacterial cells, genes move from one cell to the other
-transfer of genetic info increases genetic diversity in populations of bacteria

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Spore Formation

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-bacteria in unfavourable conditions form spores (perhaps environments undergoing succession)
-endospores formed when bacterium produce thick internal wall thaat encloses its DNA and a portion of its cytoplasm
-can remain dormant for months or years
-ability to form spores allows bacteria to survive harsh conditions that might kill them

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Viruses

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-are particles of nucleic acid, protein, and sometimes lipids
-non living
-obligate intracellular parasites(see other flash card for definition)
-specific regarding type of cells they infect
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obligate intracellular parasites

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require living hosts in order to reproduce and are unable to function outside a living host cell

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capsid

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protein coat that protects the DNA

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virion

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contains a single type of nucelic acid so either DNA or RNA

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Why are viruses non living?

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-they require living hosts in order to reproduce therefore they cannot do living processes independently
-they take advantage of host's repiration, nutrition and all other funtions
-considered as parasites

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Bacteriophage

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virus that attacks bacteria

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Lytic Infection

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process in which a virus enters a cell, makes a copy of itself and cause the cell to burst

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Lysogenic Infection

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-virus integrates its DNA into the DNA of the host cell and the biral genetic info replicates along with the host's cell's DNA

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Prophage

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viral DNA that is embedded in the host's DNA

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Lytic cycle

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-instant
-virus injects its genetic material into the host cell
-genetic material enters the nucleus and is inserted into that cell's DNA
-cell immediately begins to sue its machinery to produce the parts of future viruses
-eventually parts are assembled and cell explodes (lysis), releasing more harmful viruses

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Lysogenic cycle

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-prophage forms when phage DNA integrates into bacterial DNA
-lysogenic bacterium reproduce normally
-prophages can be induced (by mutagens) to excise from the bacterial chromosome and then enter lytic cycle

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Retroviruses

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ex. HIV
-viruses contain RNA as their genetic info
-when they infect a cell, they produce a DNA copy of their RNA
-DNA is like a prophage, and is inserted into DNA of host cell
-cell then follows the directions found in the DNA's code and eventually destroys itself (lytic cycle)
-can be dormant for a long time
-\

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Polyhedral viruses

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-many sided usually the capsid is an icosahedron (20 faces)

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Helical viruses

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-resemble long rods and their capsids are hollow cylinders surrounding the nucleic acid

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Enveloped viruses

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-may be helical or polyhedral but are often pleiomorphic (shapless)

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Complex viruses

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-have complex polyhedral head with complex tail attached
ex. bacteriophages

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Why is a Retrovirus so successful?

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-virus has done nothing therefore less energy used because makes host cell destroy itself
-cell recognises it as its own and so it doesn't know its being attacked
-only has to split to reproduce virus

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4 ways Antimicrobial drugs kill microbes

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1.enter through cell walls
2.process of translation in cell is interfered by drug
3. damaged plasma membrane (ruptured)
4. synthesis of essential metabolites is inhibited

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antimicrobial drugs

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-either kill microbe/prevent them from growing
-act inside host
-includes:syntheitic drugs and drugs provided by bacteria and funghi
-some have selective toxicity

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Vaccination

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injection of weakened form of a pathogen to produce immunity

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Vaccine

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preparation of weakened/killed pathogens
-->sometimes prompts body to produce immunity to disease

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Active immunity

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-immunity produced by the body's reaction to a vaccine
-body produces antibodies in response to antigen

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Passive Immunity

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-lasts for a shorter time b/c body eventually destroys foreign antibodies
-->when antibodies produced by other animals for a pathogen are injected into the body (ex. rabies vaccine)

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Allergies

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-most common overreactions of immune system to antigens
-most cells release histamine

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Allergen

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antigen that causes allergic reactions

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Histamine

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chemical that:
-increase flow of blood and fluids to the surrounding area
-increases mucous production in respiratory system
-causes sneezing, watery eyes , runny nose, other irritations

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Antihistamine

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-drugs that are used to counteract the effects of histamine

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Autoimmune disease

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-when immune system makes a mistake and attacks its own body cells

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HIV/AIDS

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-HIV(Human immunodeficiency virus ) = viral infection that destroys helper T-cells
-AIDS (acquired immune deficiency syndrome) = immunodeficiency disease
-number of helper t cells decline, normal immune response breaks down therefore cannot fight of colds/minor bacteria
-body is vulnerable

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How HIV attacks

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1.HIV attaches to recpetor molecules on helper T cells
2.enters cell
3.once viral core is inside cell, forces host cell to make DNA copies of viruses's RNA
4. some copies enter/insert themselves into the host cell's DNA, staying there permanently
5. other copies stay in plasm
6. can remain inactive
7. when activated, directs production of viral RNA and proteins that are assembled into new virus particles
8. eventually leave infected cell to infect others

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opportunistic disease

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disease that attacks a person with weakened immune system

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transmission HIV

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-any form of sexual intercourse
-shared needles contaminated with blood of infected person
-contact with blood products of an infected person
-infected mother to child either during pregnancy, birth, breast feeding