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Bacterial Genetics


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Transformation
may occur when bacteria directly uptake extracellular donor DNA from the environment
Transduction
donor DNA is spontaneously and unintentionally packaged in bacteriophages that infects the recipient bacterium
Conjugation
donor bacterium transfers DNA (chromosomal or plasmid) to recipient by direct cell-cell mating. Ability of sexual interaction is mediated by fertility plasmids (F+ or F-)
Homologous recombination
occurs when incoming DNA from genetic transfer is very similar to recipient genome or in the case of repairing double strand breaks.
Site-specific recombination
uses recombinases to insert donor DNA or mobile genetic elements (transposons, insertions or repeats) at specific, short DNA sequences or "sites".
Bacterial plasmids
are small, independent DNA molecules usually exchanged by transformation or congugation and often coding for specific properties, such as Abx resistance.
Ribosomal RNA
is the ultimate phylogeny molecule as it is ubiquitious in bacteria, functionally vital and thus selectively neutral (=slow to mutate), and is also easy to isolate/sequence.
Genome sequencing
can be used to find virulence genes, vaccine candidates, therapeutic candidates and phylogeny.
Antibiotic resistance
may arise when bacteria change to degrade, alter permeability to, increasingly efflux, alter binding site of, and synth. enzymes without affinity for the therapeutic agent.
Regulators
bind to promoters to increase or decrease gene transcription
Operons
contain clusters of genes regulated by a single promoter (co-regulated) that are transcribed into polycistronic mRNA (co-transcribed), which may be cleaved before translation.
Regulons
are collections of genes or operons under control of the same regulatory protein
Tryptophan
binds to the allosteric site of an otherwise inactive repressor protein, activating the catalytic site to bind to DNA and prevent transcription (gene repression)
Lactose
binds to the allosteric site of an otherwise active repressor protein, inactivating the catalytic site to free the DNA and thus allow transcription (gene activation/induction)
Virulence factors
may be regulated by change in DNA sequence (mutation, amplification or rearrangement), number of mRNA transcripts and amount of active gene product (protein) produced.
Exponential phase
produces coagulase, clumping factor, fibronectin-binding proteins, fibrinogen-binding proteins as virulence factors
Stationary phase
produces hemolysins, V8 protease, hyaluronate lyase, lipase, capsular polysaccharide and enterotoxins B/C as virulence factors
Death phase
produces enetertoxin A as a virulence factor.
Pathogenicity islands
are regions coding for virulence factors and are flanked by direct sequence repeats to promote recombination, mobility and horizontal gene transfer