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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-1626
DTSTART:20091124T180500Z
DURATION:PT1H0M0S
DTSTAMP:20260506T172200Z
LAST-MODIFIED:20090908T152715Z
LOCATION:4274 Chamberlin (Refreshments will be served)
SUMMARY:Directed evolution of ionizing radiation resistance in Escheri
 chia coli\, Chaos & Complex Systems Seminar\, Michael Cox\, UW Departm
 ent of Biochemistry
DESCRIPTION:We have generated extreme ionizing radiation resistance in
  a relatively sensitive bacterial species\, Escherichia coli\, by dire
 cted evolution. Four populations of Escherichia coli K12 were independ
 ently derived from strain MG1655\, each specifically adapted to surviv
 e exposure to high doses of ionizing radiation. D37 values for strains
  isolated from two of the populations approached that exhibited by Dei
 nococcus radiodurans. Complete genomic sequencing was carried out on n
 ine purified strains derived from these populations. Clear mutational 
 patterns were observed that both pointed to key underlying mechanisms 
 and guided further characterization of the strains. In these evolved p
 opulations\, passive genomic protection is not in evidence. Instead\, 
 enhanced recombinational DNA repair makes a prominent but probably not
  exclusive contribution to genome reconstitution. Multiple genes\, mul
 tiple alleles of some genes\, multiple mechanisms\, and multiple evolu
 tionary pathways all play a role in the evolutionary acquisition of ex
 treme radiation resistance. Several mutations in the recA gene and a d
 eletion of the e14 prophage both demonstrably contribute to and partia
 lly explain the new phenotype. Mutations in additional components of t
 he bacterial recombinational repair system and the replication restart
  primosome are also prominent\, as are mutations in genes involved in 
 cell division\, protein turnover and glutamate transport. At least som
 e evolutionary pathways to extreme radiation resistance are constraine
 d by the temporally ordered appearance of specific alleles.
URL:https://www.physics.wisc.edu/events/?id=1626
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