METALLERE VE pH STRES？NE KAR？I Escherichia coli’de RpoS’N？N ROLüNüN ARA？TIRILMASI

RpoS (σ38), which acts as an alternative sigma factor in Escherichia coli, controls the expression of genes responsible for cellular responses to different stresses including acidity, starvation, osmotic, oxidative stress, DNA damage, and stationary phase transition. In this study, the role of the rpoS gene in Escherichia coli W3110 under metals and pH stress was researched. The rpoS gene, which is a mutant in the E. coli BW25113 strain, was transferred by transduction with the P1kc phage to wild-type E. coli W3110. Life experiments in wild-type E. coli W3110 and rpoS mutant E. coli W3110 strains were carried out by plaque counting method at 3 different pH, in pH 5.5, 7.0 and 8.0 phosphate buffer. The role of rpoS in the presence of 6 different metals (Zn, Ni, Co, Cd, Ag and Cu) was also determined by the method of dropping petri. Sensitivity at rpoS mutant strains was observed at all pH values studied. It has been determined that the rpoS mutant E. coli against Cd metal shows a very significant resistance, but it has been found that there is no role in other metals. Verification of the role of the rpoS gene has been achieved by genetic complementation. These results show that the RpoS alternative sigma factor plays a role in the control of genes related to the Cd metal and in the genes associated with pH stress