Regulation of the pstSCAB operon in Corynebacterium glutamicum by the regulator of acetate metabolism RamB.

Ulrike Sorger-Herrmann,Volker F Wendisch,Hironori Taniguchi

doi:10.1186/s12866-015-0437-1

Abstract

BackgroundThe pstSCAB operon of Corynebacterium glutamicum, which encodes an ABC transport system for uptake of phosphate (Pi), is induced during the Pi starvation response. The two-component regulatory system PhoRS is involved in this response, but partial Pi starvation induction of pstSCAB in a ΔphoRS mutant indicated the involvement of additional regulator(s). Regulation of pstSCAB also involves the global transcriptional regulator GlxR.ResultsDNA affinity chromatography identified the regulator of acetate metabolism RamB as a protein binding to pstS promoter DNA in vitro. Gel mobility shift assays and mutational analysis of the pstS promoter region revealed that RamB binds to two sites localized at positions −74 to −88 and −9 to +2 with respect to the transcriptional start site of pstSCAB. Reporter gene studies supported the in vivo relevance of both binding sites for activation of pstSCAB by RamB. DNA microarray analysis revealed that expression of many Pi starvation genes reached higher levels during the Pi starvation response on minimal medium with glucose as sole carbon source than in Pi starved acetate-grown C. glutamicum cells.ConclusionsIn C. glutamicum, RamB is involved in expression control of pstSCAB operon. Thus, transcriptional regulation of pstSCAB is complex involving activation by the phosphate-responsive two-component regulatory system PhoSR and the regulators of carbon metabolism GlxR and RamB.

Highlights

The pstSCAB operon of Corynebacterium glutamicum, which encodes an ABC transport system for uptake of phosphate (Pi), is induced during the Pi starvation response
C. glutamicum wild-type strain ATCC 13032 (WT) and ΔphoRS were pre-cultured for 24 h in CGXII glucose medium without Pi in order to exhaust the intercellular phosphorus storages [25, 31] and inoculated into CGXII glucose medium with either a limiting Pi concentration of 0.065 mM or with 1 mM of the alternative phosphorus sources of adenosine 5’-monophosphate (5’AMP), L-α-glycerophosphate or UDP-glucose
With 0.065 mM Pi, which is below the Pi concentration of 0.1 mM that supported growth of C. glutamicum with a half-maximal growth rate [31], C. glutamicum WT showed a doubling time of 0.14 h−1 and formed 0.5 g DW l−1 biomass whereas the deletion mutant ΔphoRS showed a growth defect under Pi limiting conditions as expected from previous results (Table 2) [33]

Summary

Introduction

The pstSCAB operon of Corynebacterium glutamicum, which encodes an ABC transport system for uptake of phosphate (Pi), is induced during the Pi starvation response. In E. coli, the two component regulatory system PhoR-PhoB is responsible for the induction of the Pi starvation genes. Under Pi starvation conditions, the histidine kinase PhoR phosphorylates the response regulator PhoB and phosphorylated PhoB induces the transcription of at least 38 genes, the socalled PhoB regulon. Among these genes are the phoBR operon encoding two component regulatory system, the pstSCAB-phoU operon encoding an ABC transporter for high-affinity Pi uptake and an regulatory protein, and the ugpBAECQ operon encoding an sn-glycerol 3phosphate ABC uptake system and glycerophosphoryl

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