Horizontal Gene Transfer Flashcards
External genetic information is exchanged when
homologous gene recombination occurs, plasmid or bacteriophages take up residence in a new cell
Acinetobacter baumannii
is extremely prone to picking up foreign DNA, has a resistance island (cluster of drug resistant genes)
Transformation is the uptake of
naked DNA fragments from an autolysed cell
what types of cells can acquire naked DNA through transformation
naturally competent cells or forced competent cells
naturally competent cells
their genome encodes the genes for the acquisition of extracellular DNA
forced competent cells
chemical or physical treatments “force” the bacterial cell to acquire extracellular DNA (heat –>ice bath)
Transformation mechanism
naked DNA is accumulated and taken up. RecA replaces homologous sequences of donor DNA with recipient. failure to fit into a replicon (plasmid or chromosome) results in degradation
Organisms that can be transformed
H.flu, Neisseria, Staphylococcus, Streptococcus
Conjugation
horizontal transfer of a plasmid or conjugative transposon by a mechanism which it encodes for
Conjugation and transfer of R factors
mating or establishment of a sexi pili (b/w gram negative cells) followed by ssDNA of R factor is transferred through membrane pore to recipient where is it changed to dsDNA
Transduction
exchange of genetic material mediated by bacteriophages
Two types of bacteriophages
lytic phage and temperate phage
Lytic phage mechanism
generate new virion particles by: binding cell, inserting NA, replication of NA with host machinery, self assembly of gene products into virion, release of virion by lysis or slow release without lysis
Temperate phage mechanism
can act as a lytic phage OR become latent; latency is characterized by repression of lytic genes while residing as a plasmid or within the chromosome
How does latent temperate phage become active?
redepression of genes results in increased expression of genes –> lyssi
