Characterization of PlcRa, a new PlcR-like regulator involved in oxidative stress response and cysteine metabolism during early stationary phase in Bacillus cereus
Ontology highlight
ABSTRACT:
ORGANISM(S): Bacillus cereus ATCC 14579
PROVIDER: GSE30514 | GEO | 2012/12/14
SECONDARY ACCESSION(S): PRJNA143285
REPOSITORIES: GEO
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Project description:PlcR, the major virulence transcriptional regulator in the Bacillus cereus group belongs to the RNPP quorum sensor family and is activated through interaction with the secreted heptapeptide PapR7 used as a signalling molecule. We identified using modeling analysis a structural homologue of PlcR, PlcRa, in B. cereus. Whole-genome comparative microarrays identified 119 genes (threshold >3) differentially expressed at the onset of stationary phase in a plcRa mutant. phBC6A51 and phBC6A52 prophage genes were up-expressed in a plcRa mutant. Genes involved in oxidative stress response and in cysteine metabolism, including genes which belong to the CymR regulon, were down-regulated in a plcRa mutant. Accordingly, deletion of plcRa resulted in increased sensitivity to hydrogen peroxide and disulfide induced stresses. We also characterized a major target of PlcRa, the (BC2444) abrB2 gene, encoding a putative regulator belonging to AbrB family. PlcRa controlled CymR-regulated genes through AbrB2 and deletion of abrB2 gene resulted in increased sensitivity to hydrogen peroxide and disulfide induced stresses. In conclusion, we identified a new early stationary transcriptional regulator specific to B. cereus group members involved in oxidative stress response and CymR regulon activation. Two different comparisons were performed (both in biological duplo and Cy5-Cy3 dye-swapped) using 2 different time points: (1) B.cereus WT versus B. cereus plcRa overexpression strain at T1 (one hour after the onset of stationary phase) and T2 (two hours after the onset of stationary phase). (2) B.cereus WT versus B.cereus plcRa deletion strain at T1 and T2
2012-12-14 | E-GEOD-30514 | biostudies-arrayexpress
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Project description:Antimicrobial chemicals are widely applied to clean and disinfect food-contacting surfaces. However, the cellular response of bacteria, such as Bacillus cereus, to various disinfectants is unclear. In this study, the physiological and genome-wide transcriptional responses of B. cereus ATCC 14579 exposed to four different disinfectants (i.e., benzalkonium chloride, sodium hypochlorite, hydrogen peroxide, and peracetic acid) were analyzed. The physiological response of B. cereus to different concentrations of the disinfectants used was investigated. For each disinfectant, concentrations leading to the attenuation of growth, growth arrest, and cell death were studied in more detail. The simultaneous analysis of the transcriptional responses of B. cereus upon exposure to the different concentrations of disinfectants revealed common responses induced by the four disinfectants. Notably, genes involved in the general and oxidative stress responses were commonly up-regulated. Furthermore, the obtained results indicate that all the disinfectants also induce specific responses. Exposure to benzalkonium chloride, a disinfectant known to induce membrane damage, specifically induced genes involved in the fatty acid metabolism. Benzalkonium chloride induced-membrane damage was confirmed by fluorescence microscopy and fatty acid analysis confirmed that fatty acid composition of cell membrane was affected upon exposure to benzalkonium chloride. Sodium hypochlorite induced genes involved in sulfur and sulfur-containing amino acids metabolism, which correlated with the observed sodium hypochlorite-specific induction of oxidation of sulphydryl groups. Hydrogen peroxide and peracetic acid exposures induced genes involved in DNA damage and the SOS response. Notably, hydrogen peroxide and peracetic acid-treated cells exhibited higher mutation rates corroborating with the induced SOS response. Understanding the mechanisms displayed by microorganisms coping with disinfectants-induced stress may allow for design of more efficient sequential and/or disinfectant combination treatments in food processing environments.
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Project description:Transcriptional profiling of S. mutans rpoE knockout mutant comparing to the wild type. The mutation of rpoE cause dramatic changes in phenotypes. The goal is to determine the genes affected by rpoE. The delta subunit of RNA polymerase, RpoE, is wide spread in low G+C Gram-positive bacteria and is thought to play a role in enhancing transcriptional specificity by blocking RNA polymerase binding at weak-promoter sites and stimulating RNA synthesis by accelerating core enzyme recycling. Despite the well-studied biochemical properties of RpoE, a role for this protein in vivo has not been defined in depth. In this study, we show that inactivation of rpoE in the human dental caries pathogen Streptococcus mutans causes impaired growth, and loss of important virulence traits, including biofilm formation, resistance to antibiotics, and tolerance to environmental stresses. Complementation of the mutant with rpoE expressed in trans restored its phenotype to wild type. The luciferase fusion reporter showed that rpoE was highly transcribed throughout growth, and that acid and hydrogen peroxide stresses repressed rpoE expression. Transcriptome profiling of wild type and ΔrpoE cells in the exponential and early stationary phase of growth, under acid and hydrogen peroxide stress and under both stresses combined revealed that genes involved in histidine synthesis, malolactic fermentation, biofilm formation, and antibiotic resistance were down-regulated in the ΔrpoE mutant in all conditions. Moreover, the loss of RpoE resulted in dramatic changes in transport and metabolism of carbohydrates and amino acids. Interestingly, differential expression, mostly up-regulation, of 330 non-coding regions was found. In conclusion, this study demonstrates that RpoE is an important global modulator of gene expression in S. mutans, which is required for optimal growth and environmental adaptation.
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