Evidence for two recA genes mediating DNA repair in Bacillus megaterium

Abstract

Isolation and subsequent knockout of a recA-homologous gene in Bacillus megaterium DSM 319 resulted in a mutant displaying increased sensitivity to mitomycin C. However, this mutant did not exhibit UV hypersensitivity, a finding which eventually led to identification of a second functional recA gene. Evidence for recA duplicates was also obtained for two other B. megaterium strains. In agreement with potential DinR boxes located within their promoter regions, expression of both genes (recA1 and recA2) was found to be damage-inducible. Transcription from the recA2 promoter was significantly higher than that of recA1. Since a recA2 knockout could not be achieved, functional complementation studies were performed in Escherichia coli. Heterologous expression in a RecA null mutant resulted in increased survival after UV irradiation and mitomycin C treatment, proving both recA gene products to be functional in DNA repair. Thus, there is evidence for an SOS-like pathway in B. megaterium that differs from that of Bacillus subtilis.

RecA and RadA Proteins ofBrucella abortusDo Not Perform Overlapping Protective DNA Repair Functions following Oxidative Burst

“…To account for the UV resistance of the recA mutant, we hypothesized that B. abortus might express multiple RecA proteins. Both Myxococcus xanthus and Bacillus megaterium were found to carry two recA genes (38,42). The previous genetic analyses of B. megaterium had parallels to our current studies on B. abortus, since the recA mutant also exhibited moderate UV sensitivity compared to an isogenic uvrA mutant (16,38).…”

“…As documented for M. xanthus (42) and for B. megaterium (38), the expression of a "second" RecA homologue in B. abortus was considered. We reasoned that a "second" recA could partially compensate for the inactivation of the "first" recA gene, but efforts to detect or clone this postulated "second" recA in B. abortus were unsuccessful.…”

yneA mRNA instability is involved in temporary inhibition of cell division during the SOS response of Bacillus megaterium

“…However, unlike the latter, induced overexpression of YneA (Mo & Burkholder, 2010) responsible for the ICD during the SOS response as there was no detectable size increase of the yneA knockout mutant. Since B. megaterium possesses two recA genes, of which recA2 is apparently essential (Nahrstedt et al, 2005a), it is at present not feasible to check the possible interdependency with RecA, which acts, when activated by DNA damage, as a coprotease for DinR (LexA) degradation.…”

Origins and evolution of the recA / RAD51 gene family: Evidence for ancient gene duplication and endosymbiotic gene transfer

“…We performed BLAST searches for recA͞ RAD51-like genes from various organisms, especially from the species whose genomes have been completely sequenced (Table 1). We found only one recA sequence in each eubacterial species, except in two species whose recA has recently duplicated (20,21). Two recA͞RAD51 family members, RADA and RADB, were found in many archaeal species such as Archaeoglobus fulgidus and Pyrococcus abyssi.…”