Bacterial Genetics

Bacterial Genetics • Transformation • incorporation of exogenous DNA • Transduction • virally mediated gene transfer • Conjugation • pseudo-sexual reproduction One-way transfers!

Transformation • Incorporation of exogenous DNA • Bacteria must be “competent” • produce specialized proteins • competence may be triggered • DNA segments must be small • ~ 500 kb

Transformation

Transduction • Temperate virus attacks bacterium • Picks up part of bacterial chromosome when lytic • Transfers bacterial chromosome to new host

Specialized Transduction

Specialized Transduction a a

Specialized Transduction a a A

Specialized Transduction a

Conjugation • Requires donor strain and recipient strain • one-way transfer of material from donor to recipient • donor strain has F factor - a plasmid • plasmid = DNA independent of chromosome

Conjugation • During NORMAL conjugation, F factor ONLY is transferred • Some specialized types of conjugation may transfer chromosomal material also • HFR strains • High Frequency of Recombination

Conjugation Sex pillus F+ F-

Conjugation F+ F-

Conjugation F+ F+

HFR Conjugation • Parts of chromosome are donated • F factor inserts into chromosome • now called HFR mating type • HFR X F--

HFR Conjugation HFR F+

HFR Conjugation A a HFR F--

HFR Conjugation A A a HFR F--

HFR Conjugation a A x x A A a F-- HFR

Interrupted mating technique • Map bacterial loci based on timing of transfer during Hfr conjugation • Start conjugation, sample at timed intervals • Tells order, distance between loci • Need several different Hfr strains for complete map

Interrupted Mating Mapping 1 min 2 min 3 4 5 6

2 min E B 1 min 2 min A H 3 min 1 min C

Interrupted Mating Mapping

Bacterial Genetics