3-Bacteria Genetics Flashcards
genetic material
- large circular DNA chromosme, single, all genes for survival
- small circular plasmid, can be sep or integrated into chromo, rep/transferred to daughter cells
why highly regulation gene expression
- prevent waste of energy
- prevent targeting by host immune so only produce immunogenic proteins when need
- quickly respond to changing environ
operon
promoter for binding RNA polymerase
-drives expression of multi genes
regulon
genes that are regulated as a unit, multi operons being controlled at once
-one sensor/signal activates or represses multiple genes i.e heat shock
population level regulation
quorum sensing by chem molecules (autoinducers)
-sense when reach certain pop then can act certain genes to resp
vertical gene transfer
genes passed to daughter cells via replicaton
-normal process of binary fission
slower to develop antibiotic resistance than horizontal
horizontal gene transfer
- conjugation
- transformation
- transduction
homologous recombination
exchange DNA b/t two molecules based on homology aka sequence similarity
-replace chromo sequence with a similar acquired sequence
transformation
uptake of free DNA from environ
-to allow bact to gain new traits quickly
transformation mechanism
- DNA actively imported into cell
- homologous recomb, if doesnt happen then will die
conjugation
acquire new DNA directly from another living bacteria
F-factor
aka fertility factor for conjugation that carries
1. tra genes- encode sex pilus for DNA transfer
2. oriT - origin of transfer, single strand break
@plasmid or chromo
conjugation mechanism
single strand DNA transfer from donor to recipient either
1. chromosome transfer w/ homo recomb
2. plasmid transfer by normal DNA rep
conjugation recipients
only F-
no F factor
conjugation donors
Hfr (high freq of recomb)
F+
F+ x F-
conjugation
sex change of F- to F+
only single strand transferred unidirectionally
-genome not transferred just plasmid F factor
Hfr x F-
conjugation
no sex change so stays F-
tra genes not transferred so wont make sex pilli
-does have new bacterial genes
transduction
transfer of bact DNA via bacteriophage
phage life cycles
- lytic/virulent phage- replication upon entry
- temperate phage- lysogeny, will integrate into chromo, excise at some point and enter lytic
generalized transduction
accidental
-lytic phage incorps bact chromo into phage head (instead of phage genome)
when phage infects another bacteria DNA incopr into chromo via homo recomb (bc no lytic or lysogenic behavior)
specialized transduction
- lysogenic infects bacterium and integrates as prophage
- insert near gal gene
- adverse event causes excision to lytic cycle
- small part of bact chromo packaged with the phage
categories of antibiotic resistance
- intrinsic- no target
- chromo mediated
- plasmid mediated
intrinsic antibiotic characteristics
- not transferable horizontally
- no inc among populations
- lack target of the drug
chromosomal mediated characteristics
- random mutations during rep
- acquisition of resistant DNA thru horizontal transfer + incorp into genome via homo recomb
plasmid-mediated characteristics
plasmids carry genes that encode proteins
1. R-factors (resistance)
R factor components
- resistance transfer factor- equiv to F- factor, has all proteins needed for conj
- resistance determinant- gene for drug resistance
transposons
-mobile DNA elements that can transfer themselves into new molecule
transposons contain
- indirect repeat seq on each end for recognition (palindromic)
- single gene TnpA for transposase movement/jumping
- single or multi antib resistance genes
integrons
-site specific recomb (instead of homo)
-capture antibiotic gene cassettes so important for spread of multi drug resistance
integrase enzyme
pathogenicity islands
aka large transpons with virulence genes surrounded by insertion sequences
-region is acquired by horizontal
-do not encode resistance
