Rifampicin-resistant mutants of Streptomyces coelicolor A3(2).

Abstract

SUMMARY: Studies with whole cells and crude cell-free extracts of Streptomyces coelicolor a3(2) indicate that its RNA polymerase, though sensitive to rifampicin, is less so than most bacterial RNA polymerases. Of two other streptomycetes examined, one resembled S. coelicolor a3(2) and the other was more like other prokaryotes in respect of rifampicin sensitivity of its RNA polymerase. Three genetic map locations for rifampicin-resistance (rif) mutations of S. coelicolor a3(2) were determined, one (rifA) at 6 o’ clock on the conventional linkage map, very close to strA, one (rifB) at 11 o’ clock, between leuA and thiC, and a third (rifC) at 7 o’ clock, between strA and pheA. In representative rifB and C mutants, RNA synthesis was resistant to rifampicin in whole cells, but not in extracts, whereas in several rif A mutants RNA synthesis was equally resistant both in whole cells and in extracts, suggesting that the rifA gene may specify part of the RNA polymerase. None of more than 100 rifA mutants isolated possessed morphological abnormalities attributable to the rifA mutation.