RecA mediates MgpB and MgpC phase and antigenic variation in Mycoplasma genitalium, but plays a minor role in DNA repair.
Mycoplasma genitalium, a sexually transmitted human pathogen, encodes MgpB and MgpC adhesins that undergo phase and antigenic variation through recombination with archived 'MgPar' donor sequences. The mechanism and molecular factors required for this genetic variation are poorly understood. In this study, we estimate that sequence variation at the mgpB/C locus occurs in vitro at a frequency of > 1.25 × 10(-4) events per genome per generation using a quantitative anchored PCR assay. This rate was dramatically reduced in a recA deletion mutant and increased in a complemented strain overexpressing RecA. Similarly, the frequency of haemadsorption-deficient phase variants was reduced in the recA mutant, but restored by complementation. Unlike Escherichia coli, inactivation of recA in M. genitalium had a minimal effect on survival after exposure to mitomycin C or UV irradiation. In contrast, a deletion mutant for the predicted nucleotide excision repair uvrC gene showed growth defects and was exquisitely sensitive to DNA damage. We conclude that M. genitalium RecA has a primary role in mgpB/C-MgPar recombination leading to antigenic and phase variation, yet plays a minor role in DNA repair. Our results also suggest that M. genitalium possesses an active nucleotide excision repair system, possibly representing the main DNA repair pathway in this minimal bacterium.
Division of Infectious Diseases, Department of Medicine, University of Washington, Seattle, WA 98104, USA.
Raul
R
Burgos
Gwendolyn E
GE
Wood
Lei
L
Young
John I
JI
Glass
Patricia A
PA
Totten
D018829:Adhesins, Bacterial / Q000235:genetics* / Q000378:metabolism*; D000940:Antigenic Variation; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D005816:Genetic Complementation Test; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D016685:Mitomycin / Q000633:toxicity; D008969:Molecular Sequence Data; D059645:Mutation Rate; D045704:Mycoplasma genitalium / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D016133:Polymerase Chain Reaction; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism*; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014466:Ultraviolet Rays
D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D004269:DNA, Bacterial; D016685:Mitomycin; D011938:Rec A Recombinases