BACILLUS-SUBTILIS MRGA IS A DPS(PEXB) HOMOLOG - EVIDENCE FOR METALLOREGULATION OF AN OXIDATIVE-STRESS GENE

Upon the cessation of exponential growth, Bacillus subtilis enters a t ransition phase leading to either sporulation or a non-sporulating sta tionary phase. During this transition period, cells secrete degradativ e enzymes, become competent for DNA transformation, are motile and acq uire resistance to oxidative killing, We now report that mrgA, origina lly identified as a gene repressed by metal ions, encodes a member of the Dps/PexB family of general stress proteins, Like Escherichia coli Dps(PexB), MrgA forms highly stable, multimeric protein-DNA complexes which accumulate in stationary-phase cells and protect against oxidati ve killing, MrgA is part of an inducible oxidative stress response in B. subtilis: mrgA is induced by hydrogen peroxide, and a strain lackin g MrgA displays increased sensitivity to oxidative killing. In additio n, a hydrogen peroxide-resistant mutant, which constitutively overprod uces catalase and alkyl hydroperoxide reductase, also overproduces Mrg A, These results indicate a complex interplay between metal ions and t he expression of the B. subtilis oxidative stress response.