GROWTH PHASE-DEPENDENT INDUCTION OF STATIONARY-PHASE PROMOTERS OF ESCHERICHIA-COLI IN DIFFERENT GRAM-NEGATIVE BACTERIA

RSF1010-derived plasmids carrying a fusion of a promoterless lacZ gene with the sigma(s)-dependent growth phase-regulated promoters of Escherichia coli, bolAp(1) and fic, were constructed. The plasmids were mobilized into the gram-negative bacterial species Acetobacter methanolicus, Xanthomonas campestris, Pseudomonas putida, and Rhizobium meliloti. The beta-galactosidase activities of bacterial cultures were determined during exponential and stationary growth phases. Transcriptional activation of the fic promoter in the different bacteria was growth phase dependent as in E. coli and was initiated generally during the transition to stationary phase. The induction of the bolA promoter was also growth phase dependent in the bacteria tested. While the expression in E. coli and R. meliloti was initiated during the transition from exponential to stationary phase, the induction in A. methanolicus, P. putida, and X. campestris started some hours after stationary growth phase was reached. In all the species tested, DNA fragments hybridizing with the rpoS gene of E. coli were detected. The results show that in different gram-negative bacteria, stationary-phase-specific sigma factors which are structurally and functionally homologous to sigma(s) and are able to recognize the promoter sequences of both bolA and fic exist.