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Micro - general


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Describe fermentation. There are 4 things that should be noted.
*final e- acceptor is an organic cmpd
*there is no change in the redox state of the e- donor
*low energy yield
*many cycles which use many pdts that can be assayed
Describe respiration. There are 3 things that should be noted.
*final e- acceptor is an inorganic cmpd, usually O2
*e- donor changes redox state
*hi energy yield
What are siderophores? What are they used for?
They are cmpds used by bacteria to capture Fe(III)
Under what conditions do obligate anaerobes live? What is an example?
They cannot live in the presence of O2. E.g. gut flora.
Under what conditions do aerotolerant anaerobes live?
They can live in the presence or absence of O2, but grow best in its absence.
Under what conditions do facultative anaerobes live?
They are able to live in the presence or absence of O2, but grow best in its presence.
Under what conditions do obligate aerobes live?
They can grow only in the presence of O2.
Under what conditions do microaerophiles live?
They grow only in the presence of small amounts of O2.
What is the equation to predict the number of bacteria at time = t?
Nt = No2^(t/T)
No = initial number of bacteria
t = time
T = generation time
Describe the life cycle of lytic phages.
*invade baacterium
*begin replication using host machinery
*host swells and lyses, releasing a new generation of phages
Describe the life cycle of lysogenic phages.
*invade bacterium
*integrate DNA into host genome
*DNA is replicated with host genome and passed to progeny
*activated by certain stresses - enter lytic cycle
What kind of recombination involves the overlap of a single strand? Of both strands?
Homologous involves the overlap of a single strand while nonhomologous involves both strands.
What is homologous recombo based on?
Sequence similarity.
A bacterium undergoes homologous recombo with a piece of phage DNA. Describe the genetic makeup of of this bacterium's two daughter cells (after recombo)?
One daughter will have 2 srands of the parental DNA, and the other will have a double stranded section of the phage insert.
What is the end result of nonhomologous recombo? How is it done?
A double-stranded piece of foreign DNA is inserted. This is done enzymatically.
What is specialized transduction?
A phage delivers only that DNA which flanked its insertion site on the donor genome.
What is generalized transduction?
A phage will transfer any piece of DNA between two bacteria.
What is transformation?
Bacterial uptake of naked DNA.
What is conjugation? How is it usually mediated? What specialized thing is often involved?
*transfer of DNA between bacteria via direct cell-cell contact
*usually mediated by plasmids
*may or may not involve a pilus
Name two ways antibiotic resistance is acquired by bacteria.
1.Chromosomal mutation
2.Picking up R factors from plasmids, phages, or fom another bacteria.
What are 3 general strategies for antibiotic resistance?
1.Modify or inactivate the drug
2.Modify the target of the drug
3.Deny access to the drug
What is the S-layer? What is its function?
An external structure that is a crystalline array of a single protein type. It protects the bacterium.
What are the 2 forms a polysaccharide layer can take? What does each do?
1.Capsule: provides protection, slippery surface is anti-phagocytic
2.Slime layer (glycocalyx): allows attachment to solid surfaces
What is the structure and function of pili? Where are they anchored?
Filiments of pilin anchored in the outer membrane that function in attachment.
What do flagella do? Where are they anchored?
*function is locomotion
*anchored in the plasma membrane
Name 4 things that can serve as antigens. 3 of them have letter codes.
1.flagella - H Ag
2.LPS - O Ag
3.capsule - K Ag
4.teichoic/teichuronic acids
What are the 5 stages of biofilm development?
1.Adsorption of microbes
2.Irreversible attachment
3.Growth & division
4.EPS and biofilm formation
5.Attachment of other bugs
Name 3 ways normal flora provide protection against pathogens.
1.Physical blocking
2.Synth of inhibitory cmpds
3.Stimulation of host defenses
What are 4 mediators of endotoxic shock?
1.Lipid A/LPS (on G- only)
4.Other sugars
What are 4 members of the TLR family and what do they bind?
1.TLR-4: LPS
2.TLR-2: peptidoglycan
3.TLR-5: flagella
4.TLR-9: bacterial DNA
What are Koch's postulates? (3)
1.Isolate bacteria from sick pt
2.Grow bacteria in pure culture
3.Infect another animal with isolate
What are 3 diffiiculties in the use of BT agents?
1.Hard to produce highly transmissible forms.
2.Some require high inoculum and have no p-p spread
3.Agents with p-p spread are impossible to control
Most exogenous nosomial pathogens are G+.
False: most exogenous nosocomial pathogens are G-
What are 2 aspects that make exogenous nosocomial pathogens difficult to deal with?
1.Able to withstand harsh conditions
2.Multi-drug resistance
What are 4 things that make BT agents dangerous?
1.Readily available
2.Inexpensive to produce
3.Easy to transport
4.Not easily detectable
(5.Incubation time can make it difficult to determine time and place of release)

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