gene expression, transfer and resistance Flashcards
why do bacteria adapt quickly to change
- different metabolic pathways
- multicomponent structures
what are the various triggers to gene expression
- temperature
- osmolarity
- pH
- nutrient availability
- oxygen
- iron
where is salmonella found
- GI tract or endosomal vesicle within a macrophage
what conditions does salmonella require
high osmolarity and low oxygen
what activates gene expression in salmonella
pathogenicity island and invasion genes
where is e.coli found
edit of gut
what conditions does e.coli inactivate gene expression
drop in temperature inactivates adherence genes
what e.coli conditions activate gene expression
low iron levels activates haemolysin that kills cells and provides iron
what conditions of Corynebacterium diphtheriae
activates gene expression
low iron levels activates diphtheria toxin that kills cells and provides iron
what is special about bacteria DNA and RNA
- no nuclear membrane
- no need for nuclear mRNA export
- ribosomes bind to mRNA during transcription
what is expression regulated by in bacteria
transcription
what does promotors do
recognised by sigma factors that regulate gene/operon expression
what does substrates do to expression
induces expression - increases expression of metabolic enzymes
what does the end product to do expression
repression by reducing enzyme synthesis
what are operons
group of related genes under a promoter
what does lac operon do
- turns off in presence of glucose
- turns on in presence of lactose metabolite or inducer
what happens in e.coli lactose metabolism
turned off in presence of glucose - repressor binds to operator reducing RNA polymerase
what happens in e.coli tryptophan biosynthesis
- too much can be toxic
- five enzymes necessary
- control via operator - repression binds to operator inhibiting it
- leader gene - loop termination of mRNA synthesis
what does phase variable require in c.diff
RecV for gene switching
what is formed when CWPV switch in c.diff is on
cwpV-CTD and cwpV-FL
what is quorum sensing
coordinated expression of genes in a colony
what does pseudomonas do in quorum sensing
biofilm produced triggering N-acyl homoserine lactone (AHL)
what does staph aureus do in quorum sensing
biofilm and toxin produced triggered by cyclic peptide
what are pathogenicity islands
- virulence mechanism operon
- 10-200Kb mobile elements
