Bacteriology 1.2 Flashcards
gene expression regulation
temp, ph, IRON, carbon, nitrogen, osmolarity, oxygen, etc.
how do bacteria regulate transcription?
transcription factors.
stimulus> activation/inhibition of trans regulator>activation/in of target genes
Always exons!
single gene
look up
regulon
a collection of genes or operons under regulation by the same regulatory protein.
operon
a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter.
Diphtheris toxin expression
prophage integrated. DtxR binds iron and DNA, prevents transcription.
Red queen hypothesis
keep running to stay in place.
ability of bacteria to change their genetic attributes, key to their success.
cat and mouse with immune system.
mechanisms of genetic change and diversity
mutations.
gene duplication
gene deletion
chromosomal rearrangement- inversion, intragenic recombo
in 70 generations a bacterium can replicate to produce 10^21 cells
Point mutation
impact expression of virulence factors and sensitivity of antibiotic targets (fitness cost)
can become hypermutable during stress
gene duplication
can lead to amplification of gene product that can provide resistance to antibiotic.
mechanism by which many bacteria are resist to sulfonamides and beta lactams.
Phase variation
a way to change some characteristic like turn on/off pili. alter surface structure that make them more or less visible.
happen randomly
regulation of capsule expression
look up
phase variation by gene conversion
neisseria, excess copies that can recombine and give new domains. mismatch of antigens that can be expressed.
bacteria makes it so that it doesn’t get detected by antibody.
phase variation by slipped-strand synthesis
pertussis- BvgA, can turn on/off by slipstrand synth. introduced new base pairs, like a point.
phase variation by promoter inversion
make type 1 pili, for attachment. not virulent without pili.
encoded by fim gene, promoted by fimS. only works in reverse direction turns on and off.
Horizontal gene transfer HGT
bacterial transformation, give others their DNA.
1. Transformation
2. Transduction
3. Conjugation
thought to be random, but increased by factor of 25 in gut
Transformation
funeral, eat corpse and get their eye color.
acquire traits by eating
Griffith’s 1928 experiment. S. pneumoniae. S strain virulence factor transferred into R strain. =transformation.
transduction
catching a cold from someone with blue eyes, then your eyes turn blue.
mediated by bacteriophages.
conjugation
two bacteria hook up, transfer plasmids or chromosome pieces. bacterial sex
you get blue eyes by sleeping with someone with blue eyes.
F cell ** look up
competence
ability to take up DNA, bacillus subtitles and s. pneumoniae are really good. mostly only linear DNA
Bacteriophage
injects DNA into bacteria, can be extra or intra chromosomal through lysogenize.
lytic phase
.
lysogenic phase
.
generalized transducing phage
look up.
transfer DNA during lytic phase. can accidentally package part of bacterial genome
specialized transducing phage
becomes prophage initially, when it goes to lytic cycle it will replicate and excise itself.
plasmids
r plasmids, carry resistance
transposons
DNA elements that move from one place in bacterial DNA to another.
can transfer genes to a new location or disrupt genes when inserting
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