Involvement of motility and flagella in Bacillus cereus biofilm formation

Production, secretion and biological activity of Bacillus cereus enterotoxins

Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.

Transcriptomic responses of Salmonella enterica serovars Enteritidis and Typhimurium to chlorine-based oxidative stress

Salmonella enterica serovars Enteritidis and Typhimurium are the leading causative agents of salmonellosis in the United States. S. Enteritidis is predominantly associated with contamination of shell eggs and egg products, whereas S. Typhimurium is frequently linked to tainted poultry meats, fresh produce, and recently, peanut-based products. Chlorine is an oxidative disinfectant commonly used in the food industry to sanitize the surfaces of foods and food processing facilities (e.g., shell eggs and poultry meats). However, chlorine disinfection is not always effective, as some S. enterica strains may resist and survive the disinfection process. To date, little is known about the underlying mechanisms of how S. enterica responds to chlorine-based oxidative stress. In this study, we designed a custom bigenome microarray that consists of 385,000 60-mer oligonucleotide probes and targets 4,793 unique gene features in the genomes of S. Enteritidis strain PT4 and S. Typhimurium strain LT2. We explored the transcriptomic responses of both strains to two different chlorine treatments (130 ppm of chlorine for 30 min and 390 ppm of chlorine for 10 min) in brain heart infusion broth. We identified 209 S. enterica core genes associated with Fe-S cluster assembly, cysteine biosynthesis, stress response, ribosome formation, biofilm formation, and energy metabolism that were differentially expressed (>1.5-fold; P < 0.05). In addition, we found that serovars Enteriditis and Typhimurium differed in the responses of 33 stress-related genes and 19 virulence-associated genes to the chlorine stress. Findings from this study suggest that the oxidative-stress response may render S. enterica resistant or susceptible to certain types of environmental stresses, which in turn promotes the development of more effective hurdle interventions to reduce the risk of S. enterica contamination in the food supply.

Identification of trans- and cis-control elements involved in regulation of the carbon monoxide dehydrogenase genes in Mycobacterium sp. strain JC1 DSM 3803

The cutR gene was identified 314 bp upstream of the divergently oriented cutB1C1A1 operon encoding carbon monoxide (CO) dehydrogenase in Mycobacterium sp. strain JC1. Its deduced product was composed of 320 amino acid residues with a calculated molecular mass of 34.1 kDa and exhibits a basal sequence similarity to the regulatory proteins belonging to the LysR family. Using a cutR deletion mutant, it was demonstrated that CutR is required for the efficient utilization of CO by Mycobacterium sp. strain JC1 growing with CO as the sole source of carbon and energy. CutR served as a transcriptional activator for expression of the duplicated cutBCA operons (cutB1C1A1 and cutB2C2A2) and was involved in the induction of the cutBCA operons by CO. The cutBCA operons were also subjected to catabolite repression. An inverted repeat sequence (TGTGA-N(6)-TCACA) with a perfect match with the binding motif of cyclic AMP receptor protein was identified immediately upstream of and overlapping with the translational start codons of cutB1 and cutB2. This palindrome sequence was shown to be involved in catabolite repression of the cutBCA operons. The transcription start point of cutR was determined to be the nucleotide G located 36 bp upstream of the start codon of cutR. Expression of cutR was higher in Mycobacterium sp. strain JC1 grown with glucose than that grown with CO.

CwpFM (EntFM) is a Bacillus cereus potential cell wall peptidase implicated in adhesion, biofilm formation, and virulence

Bacillus cereus EntFM displays an NlpC/P60 domain, characteristic of cell wall peptidases. The protein is involved in bacterial shape, motility, adhesion to epithelial cells, biofilm formation, vacuolization of macrophages, and virulence. These data provide new information on this, so far, poorly studied toxin and suggest that this protein is a cell wall peptidase, which we propose to rename CwpFM.