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32 Cards in this Set
- Front
- Back
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What is fermentation?
What is the simplest fermentation pathway? |
Anaerobes use carbohydrates as their terminal electron receptor to produce ATP (as opposed to oxygen in aerobles)
Homolactic acid pathway: 1 glucose + 2 ADP --> 2 lactic acid + 2 ATP |
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What are 2 toxic metabolites that are produced during metabolism in the presence of oxygen?
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Hydrogen peroxide and superoxide anion
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What are the 2 enzymes and reactions that detoxify the products of metabolism in the presence of oxygen?
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catalase: 2H2O2 --> 2H2O + O2
SOD: O2- + 2H+ --> H2O2 + O2 |
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Presence of catalase and SOD:
1. Aerobes 2. Anaerobes 3. Faculatative anaerobes 4. Microaerophiles |
1. catalase, SOD
2. - 3. SOD and catalase 4. SOD, fermentive |
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How do bacteria obtain iron from host cells?
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Release siderophores (Fe-chelators) --> compete with lactoferrin, ferritin, transferrin, and Hb for iron --> bring back to bacteria
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Temperature ranges
a. Psychrophiles 2. Mesophiles 3. Thermophiles |
a. 0-25; opt. 10-15
b. 15-45; opt. 30-37 --> infect humans c. 35-70; opt. 55 |
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How do prokaryotes reproduce? What is formed?
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Binary fission --> 2 identical daughter clones
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What are 3 indirect methods of measuring bacterial growth?
1 direct method? |
Turbidity, dry weight, bacterial N
Viable or plate count |
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What are 4 phases of bacterial culture growth?
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1. Lag - adjustment to new media, cell size small
2. Log - constant doubling rate, large cell size 3. Staionary - growth=death, limiting nutrients, small cell size 4. death - Deccrease rapidly , small cell size |
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How is protein synthesis and expression regulated during the phases of bact. growth?
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different sigma factors bind with RNA polymerase --> holoenzyme targets different genes
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What is the difference between sterilization and disinfection?
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Sterilization = complete absence of life
Disinfection = Killing potentially pathogenic microorganisms |
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What are 4 physical methods of sterilization?
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1. Autoclave - moist heat
2. UV Radiation 3. Filtration 4. Asepsis - maintains sterility |
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What are 8 chemical agents used in the lab to disinfect?
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1. 70% ethanol - disrupts membranes
2. detergents - disrupts membranes 3. phenols - denatures proteins, cell membrane 4. halogen - oxidizes 5. Heavy metals - bind to sulfhydryl groups, block enzyme activity 6. hydrogen peroxide - oxidizing agent 7. Formaldehyde and gluaraldehyde - alkylating agents 8. Ethylene oxide - alkylating agent |
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What is a merodiploid state?
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Bacteria has 2 copies of only 1 gene (one was exogenously introduced)
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What is a reversion mutation?
Suppression mutation? |
Reversion = After one mutation, a second spontaneous mutation that converts it back to the original codon or a redundant codon
Suppression = after one mutation, a second mutation that codes for another amino acid but does not affect the function of the protein |
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Homologous recombination
a. region of homology b. RecA product required c. Sequence-specific enzyme required |
a. Large
b. Yes c. No |
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Site-specific recombination
a. region of homology b. RecA product required c. Sequence-specific enzyme required |
a. small
b. no c. yes |
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Insertion sequences/transposons
a. region of homology b. RecA product required c. Sequence-specific enzyme required |
a. very small
b. no c. yes |
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Illegitimate recombination
a. region of homology b. RecA product required c. Sequence-specific enzyme required |
a. no
b. no c. ? |
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How does homologous recombination work?
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-RecA aligns two similar sequences
-2 crossovers (linear) or 1 (circular) -Excised DNA either lost or becomes a plasmid (if it contains a replicon) |
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What is the role of recombinase in site-specific recombination?
What is the result? |
Recombinase finds sequence, performs cross-over
If plasmid or phage --> net gain of DNA to bacteria |
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What is a transposon?
What does it require? |
Genetic elements that can hop to different places on DNA --> can confer Ab resistance
Requires site-specific recombinase --> transposase |
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What is a natural transformation?
What is induced transformation? |
Uptake of naked DNA by naturally competent bactria, followed by homologous recombination (incorp. DNA into genome)
Bacteria must be made to be competent using high salt conc. or electroporation |
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What is conjugation?
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Sexual mating = direct contact through a pilus to exchange a plasmid
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What is the difference between a conjugative plasmid and a non-conjugative plasmid?
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conjugative = able to transfer to other bacteria, low copy number
Non-conjugative = unable to transfer, high copy number |
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What is sexduction using the F factor?
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F+ bacteria transfer F plasmid to F-minus bacteria through pilus, making them also F+
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What is an Hfr? What are 3 possible fates of an Hfr?
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Hfr = high frequency recomination = a chromosome with an integrated F plasmid
1. Can excise the plasmid perfectly for further conjugation 2. Can excise the plasmid imperfectly, so that when conjugation occurs, F plasmid plus a piece of chromosome goes 3. Conjugation DIRECTLY from chromosome, time dependent transfer of genome |
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How do non-conjugative plasmids transfer (lack genes necessary for transfer) ?
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Can be helped by a helper plasmid that provides transfer factors
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What are conjugative transposons?
Self transfer? Mobilization? |
Conjugative transposons - have the ability to transfer themselves to a recipient strain via conjugation
self transfer = movement into new cell and integration mobilization = transposon moves with a co-resident plasmid by either donating its transfer machinery to plasmid, or incorporating into the plasmid and moving as a whole |
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Transduction?
What must a transducing phage package |
The ability of a bacteriophage to carry chromosomal DNA from one donor cell to a newly infected recipient cell
Transducing phage must package DNA |
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What are 2 life cycles of temperate phages?
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1. Lytic - accumulation of new phage particles --> cell lysis
2. Lysogenic phage - integration of prophage (genome) --> lysogen --> dormant until cell is stressed --> lytic Lysogen is immune from second infection |
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What is phage conversion?
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When a temperate phage carries genes encoding virulence factors AND normal phage genes --> formation of a lysogen my convert non-pathogenic bacteria into pathogenic
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