The thiol oxidation-based sensing and regulation mechanism for the OasR-mediated organic peroxide and antibiotic resistance in C. glutamicum

Abstract

Corynebacterium glutamicum, an important industrial and model microorganism, inevitably encountered stress environment during fermentative process. Therefore, the ability of C. glutamicum to withstand stress and maintain the cellular redox balance was vital for cell survival and enhancing fermentation efficiency. To robustly survive, C. glutamicum has been equipped with many types of redox sensors. Although cysteine oxidation-based peroxide-sensing regulators have been well described in C. glutamicum, redox sensors involving in multiple environmental stress response remained elusive. Here, we reported an organic peroxide- and antibiotic-sensing MarR (multiple antibiotics resistance regulators)-type regulator, called OasR (organic peroxide- and antibiotic-sensing regulator). The OasR regulator used Cys95 oxidation to sense oxidative stress to form S-mycothiolated monomer or intermolecular disulfide-containing dimer, resulting in its dissociation from the target DNA promoter. Transcriptomics uncovered the strong up-regulation of many multidrug efflux pump genes and organic peroxide stress-involving genes in oasR mutant, consistent with the phenomenon that oasR mutant showed a reduction in sensitivity to antibiotic and organic peroxide. Importantly, the addition of stress-associated ligands such as cumene hydroperoxide and streptomycin induced oasR and multidrug efflux pump protein NCgl1020 expression in vivo. We speculated that cell resistance to antibiotics and organic peroxide correlated with stress response-induced up-regulation of genes expression. Together, the results revealed that OasR was a key MarR-type redox stress-responsive transcriptional repressor, and sensed oxidative stress generated through hydroxyl radical formation to mediate antibiotic resistance in C. glutamicum.

Involvement of a mycothiol-dependent reductase NCgl0018 in oxidative stress response of <i>Corynebacterium glutamicum</i>

“…glutamicum (Si et al, 2020). Moreover, M. tuberculosis Rv2466c was validated to promote mycobacterial resistance to oxidative stress (Rosado et al, 2017).…”

“…S5). Recently, Si et al (2020), found that NCgl0018 was also one of the main targets of OasR by microarray analysis, which is strongly linked to the oxidative stress response in C. glutamicum. Therefore, we further detected OasR's regulatory capacity for NCgl0018.…”

“…Recently, Si et al (2020), reported that C. glutamicum OasR (organic peroxide-and antibiotic-sensing regulator), a MarR family regulatory protein, negatively controlled the expression of ncgl0018 gene encoding an oxidoreductase enzyme annotated as the putative DsbA of C. glutamicum. Although NCgl0018 was supposed to be another candidate in the antioxidant system of bacteria, its physiological functions have not been experimentally confirmed in C. glutamicum.…”

OsnR is an autoregulatory negative transcription factor controlling redox-dependent stress responses in Corynebacterium glutamicum

“…Logically, cells exposed to diamide will downregulate OsnR, due to transcriptional repression of the osnR gene by its own protein, thereby de-repressing the stressresponsive genes. In addition, changes in cellular redox status can cause structural modification of the OsnR protein through cysteine residues, resulting in changes in the activity and functional properties of the protein, as such mechanism was proposed for other regulators, such as CosR (C49 and C62), MsrR (C62), OasR (C95), OhsR (C125), OxyR (C199 and C208), RosR (C92), and QorR (C17) [25][26][27][28][29][30][49][50][51]. The OsnR protein has two cysteine residues (C2 and C10) at the N-terminus, and these residues may function as a thiol-based redox switch to respond to cellular redox status.…”

“…Moreover, many of these proteins contain cysteine residues in a configuration that may respond to cellular redox signals, thereby regulating cognate stressresponsive genes. These cysteine-containing regulators in C. glutamicum include WhcE and WhcA [22,23], OxyR [8,24], OhsR [25], RosR [26], MsrR [27], CosR [28], QorR [29], OasR [30], and OsrR [31]. In addition, along with the master regulator SigH [32,33], multiple regulatory proteins also participate directly or indirectly in the regulation of oxidative-stress responses [34,35].…”