1887

Abstract

We previously showed that in , accumulation of polyhydroxybutyrate (PHB) occurs mainly during the stationary phase, and that a mutation in , encoding a transcriptional regulator of the AraC family, reduces PHB accumulation. In this study, we characterized the roles of PhbR and RpoS, a central regulator during stationary phase in bacteria, in the regulation of expression of the PHB biosynthetic operon and We showed that inactivation of reduced PHB accumulation, similar to the mutation, and inactivation of both and resulted in an inability to produce PHB. We carried out expression studies with the wild-type, and the , and double - mutant strains, using quantitative RT-PCR, as well as  : :  and  : :  gene fusions. These studies showed that both PhbR and RpoS act as activators of and , and revealed a role for PhbR as an autoactivator. We also demonstrated that PhbR binds specifically to two almost identical 18 bp sites, TGTCACCAA-N-CACTA and TGTCACCAA-N-CAGTA, present in the promoter region. The activation of and transcription by RpoS reported here is in agreement with the observation that accumulation of PHB in occurs mainly during the stationary phase.

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2011-11-01
2019-09-23
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