Miura K, Inouye S, Nakazawa A
Department of Biochemistry, Yamaguchi University School of Medicine, Ube, Japan.
Mol Gen Genet. 1998 Jul;259(1):72-8. doi: 10.1007/s004380050790.
Operon OP2 on the Pseudomonas putida TOL plasmid encodes enzymes for m-toluate catabolism; transcription of this operon is activated by XylS in the presence of m-toluate. Because transcriptional activation of OP2 specifically occurs in the stationary phase of growth both in P. putida and in Escherichia coli, we suspected that its transcription is dependent on RpoS (sigmaS). Therefore, we constructed a rpoS disruption strain of P. putida mt-2, and assayed OP2 expression and other phenotypes. OP2 transcription was dependent on rpoS, indicating that the stationary-phase specific activation of OP2 is due to positive regulation by RpoS in P. putida mt-2. The rpoS mutant exhibited reduced viability during the stationary phase and was sensitive to high salt concentrations and H2O2. P. putida mt-2 has two catalase isozymes, KatA and KatB. Expression of the katB gene was specific to the stationary phase and entirely dependent on the rpoS gene, while the katA gene expressed during log phase partially required rpoS. There were no significant changes in tolerance to high temperature or UV light in the rpoS mutant. No difference was observed between the E. coli rpoS mutants and their parents in their capacity to activate OP2, suggesting that the mechanism of OP2 activation in the stationary phase of growth differs between P. putida and E. coli.
恶臭假单胞菌TOL质粒上的操纵子OP2编码间甲苯酸分解代谢所需的酶；在间甲苯酸存在的情况下，该操纵子的转录由XylS激活。由于OP2的转录激活在恶臭假单胞菌和大肠杆菌的生长稳定期均特异性发生，我们怀疑其转录依赖于RpoS（σS）。因此，我们构建了恶臭假单胞菌mt-2的rpoS缺失菌株，并检测了OP2的表达及其他表型。OP2转录依赖于rpoS，这表明在恶臭假单胞菌mt-2中，OP2在稳定期的特异性激活是由于RpoS的正调控。rpoS突变体在稳定期的生存能力降低，并且对高盐浓度和H2O2敏感。恶臭假单胞菌mt-2有两种过氧化氢酶同工酶，KatA和KatB。katB基因的表达特异性地发生在稳定期，并且完全依赖于rpoS基因，而对数期表达的katA基因部分需要rpoS。rpoS突变体在耐高温或紫外线方面没有显著变化。在激活OP2的能力方面，大肠杆菌rpoS突变体与其亲本之间未观察到差异，这表明恶臭假单胞菌和大肠杆菌在生长稳定期激活OP2的机制不同。
