Deciphering the essentiality and function of the anti‐σ^M factors in Bacillus subtilis

Abstract

Bacteria use alternative sigma factors to adapt to different growth and stress conditions. The Bacillus subtilis extracytoplasmic function sigma factor SigM regulates genes for cell wall synthesis and is crucial for maintaining cell wall homeostasis under stress conditions. The activity of SigM is regulated by its anti-sigma factor, YhdL, and the accessory protein YhdK. Here, we show that dysregulation of SigM caused by the absence of either component of the anti-sigma factor complex leads to toxic levels of SigM and severe growth defects. High SigM activity results from a dysregulated positive feedback loop, and can be suppressed by overexpression of the housekeeping sigma, SigA. Using a sigM merodiploid strain, we selected for suppressor mutations that allow survival of yhdL depletion strain. The recovered suppressor mutations map to the beta and beta-prime subunits of RNA polymerase core enzyme and selectively reduce SigM activity, and in some cases increase the activity of other alternative sigma factors. This work highlights the ability of mutations in RNA polymerase that remodel the sigma-core interface to differentially affect sigma factor activity, and thereby alter the transcriptional landscape of the cell.

The anti-sigma factor MucA is required for viability inPseudomonas aeruginosa

“…The concentrations and affinities of individual sigma factors influence their competition for the core RNAP [59,60]. While sigma factor competition is best studied in E. coli, it has been observed in other organisms, including P. aeruginosa [47,59,[61][62][63]. One such example in P.…”

From Modules to Networks: a Systems-Level Analysis of the Bacitracin Stress Response in Bacillus subtilis

“…Expression of BcrC is primarily controlled by the extracytoplasmic function sigma factor M (14,30). While the physiological input triggering activation of M still remains elusive (31,32), the broad range of inducing conditions, including cell wall antibiotics, salt, ethanol, and others, suggests that it is not a specific chemical compound but rather a cellular cue upon cell envelope damage that activates the M response (33). Interestingly, despite the seemingly unrelated input stimuli for the BceAB and the BcrC resistance modules-with BceAB being activated by a "drugsensing" mechanism (antibiotic flux) and BcrC by a "damage-sensing" mechanismprevious work revealed that there is a high level of interdependency between the modules (26).…”

Mutations of the Bacillus subtilis YidC1 (SpoIIIJ) insertase alleviate stress associated with σM-dependent membrane protein overproduction

“…However, full YhdL activity requires a second transmembrane protein, YhdK. Although a lack of σ M is well tolerated under unstressed conditions, the lack of the anti-σ M factors leads to a runaway activation of the autoregulated sigM operon, and overexpression of the σ M regulon [10]. A null mutation of yhdK leads to an ~100-fold elevation of σ M activity, morphological abnormalities, and slow growth [10].…”

“…Although a lack of σ M is well tolerated under unstressed conditions, the lack of the anti-σ M factors leads to a runaway activation of the autoregulated sigM operon, and overexpression of the σ M regulon [10]. A null mutation of yhdK leads to an ~100-fold elevation of σ M activity, morphological abnormalities, and slow growth [10]. A null mutation in yhdL is lethal, but suppressors arise readily that have inactivated sigM and grow normally in unstressed conditions [4, 10].…”