Two MarR-Type Repressors Balance Precursor Uptake and Glycine Betaine Synthesis in Bacillus subtilis to Provide Cytoprotection Against Sustained Osmotic Stress.

摘要: Bacillus subtilis adjusts to high osmolarity surroundings through the amassing of compatible solutes. It synthesizes solute glycine betaine from prior imported choline and scavenges many pre-formed osmostress protectants, including betaine, environmental sources. Choline is substrate-restricted ABC transporter OpuB closely related, but promiscuous, OpuC system, followed by its GbsAB-mediated oxidation betaine. We have investigated impact two MarR-type regulators, GbsR OpcR, on gbsAB, opuB, opuC expression. Judging position previously identified OpcR operator in regulatory regions opuB [Lee et al. (2013) Microbiology 159, 2087-2096], that current study, we found related repressors use different molecular mechanisms control transcription. functions sterically hindering access RNA-polymerase promoters, while operates a roadblock mechanism gbsAB Loss or de-represses transcription, respectively. With respect osmotic expression, this cue independently regulators. When assessed over wide range salinities, exhibit surprisingly transcriptional profile. Expression increases monotonously response incrementally increase salinity, transcription levels decrease after an initial up-regulation at moderate salinities. Transcription gbsR opcR genes up-regulated salt stress, also affected auto-regulatory processes. The operons evolved gene duplication event. However, evolution has shaped their mode genetic regulation, osmotic-stress dependent profile, substrate specificity transporters distinctive fashion.