1,721,950 research outputs found
Role of germinant receptors in Caco-2 cell-initiated germination of Bacillus cereus ATCC 14579 endospores
No full textSpores obtained from Bacillus cereus ATCC 14579 and mutant strains lacking each of seven germinant receptor operons were exposed to differentiated Caco-2 cells and monitored for germination. Spores of the gerI and gerL mutants showed a reduced germination response, pointing to a role for these receptors in Caco-2- induced germination
Direct-Imaging-Based Quantification of Bacillus cereus ATCC 14579 Population Heterogeneity at a Low Incubation Temperature
No full textBacillus cereus ATCC 14579 was cultured in microcolonies on Anopore strips near its minimum growth temperature to directly image and quantify its population heterogeneity at an abusive refrigeration temperature. Eleven percent of the microcolonies failed to grow during low-temperature incubation, and this cold-induced population heterogeneity could be partly attributed to the loss of membrane integrity of individual cells
Phenotypic and Transcriptomic Analyses of Mildly and Severely Salt-Stressed Bacillus cereus ATCC 14579 Cells
No full textBacteria are able to cope with the challenges of a sudden increase in salinity by activating adaptation mechanisms. In this study, exponentially growing cells of the pathogen Bacillus cereus ATCC 14579 were exposed to both mild (2.5% [wt/vol] NaCl) and severe (5% [wt/vol] NaCl) salt stress conditions. B. cereus continued to grow at a slightly reduced growth rate when it was shifted to mild salt stress conditions. Exposure to severe salt stress resulted in a lag period, and after 60 min growth had resumed, with cells displaying a filamentous morphology. Whole-genome expression analyses of cells exposed to 2.5% salt stress revealed that the expression of these cells overlapped with the expression of cells exposed to 5% salt stress, suggesting that the corresponding genes were involved in a general salt stress response. Upregulation of osmoprotectant, Na+/H+, and di- and tripeptide transporters and activation of an oxidative stress response were noticeable aspects of the general salt stress transcriptome response. Activation of this response may confer cross-protection against other stresses, and indeed, increased resistance to heat and hydrogen peroxide could be demonstrated after preexposure to salt. A temporal shift between the transcriptome response and several phenotypic responses of severely salt-stressed cells was observed. After resumption of growth, these cells showed cellular filamentation, reduced chemotaxis, increased catalase activity, and optimal oxidative stress resistance, which corresponded to the transcriptome response displayed in the initial lag period. The linkage of transcriptomes and phenotypic characteristics can contribute to a better understanding of cellular stress adaptation strategies and possible cross-protection mechanism
Impact of sorbic acid on germinant receptor-dependent and -independent germination pathways in Bacillus cereus
No full textAmino acid- and inosine-induced germination of Bacillus cereus ATCC 14579 spores was reversibly inhibited in the presence of 3 mM undissociated sorbic acid. Exposure to high hydrostatic pressure, Ca-dipicolinic acid (DPA), and bryostatin, an activator of PrkC kinase, negated this inhibition, pointing to specific blockage of signal transduction in germinant receptor-mediated germination
Bacillus cereus acid stress responses
No full textBacillus cereus is a ubiquitous Gram-positive organism, which frequently causes foodborne illnesses. The widespread prevalence of B. cereus makes it a common contaminant in fresh foods where it also can cause spoilage. To prevent food-borne diseases and food spoilage, foods are often processed and/or preserved. In recent years, consumers’ preferences have directed to fresher and tastier foods and this has acted as a driver for food industry to use milder processing and preservation techniques. Examples of hurdles that can be applied to preserve foods are low pH and the addition of organic acids. B. cereus may overcome these adverse conditions by displaying an adaptive stress response. The response of B. cereus upon exposure to these hurdles was investigated using two model strains, ATCC 14579 and ATCC 10987. Comparative analysis revealed numerous strain-specific genes and differences in metabolic capacities, including a urease encoding gene cluster in ATCC 10987 and a nitrate respiration cluster in ATCC 14579. A survey including ATCC 10987 and 48 environmental and outbreak-associated isolates revealed urease activity, i.e., the conversion of urea in ammonia and carbon dioxide, to be present in 10 isolates. However, the activity appeared to be too low to contribute to acid resistance in the strains tested. To search for other acid resistance mechanisms, comparative phenotype and transcriptome analyses of strains ATCC 14579 and ATCC 10987 cells exposed to organic and/or inorganic acid shocks were performed. Upon exposure to low pH with or without the addition of lactic acid or acetic acid, common acid resistance mechanisms and induction of the nitrate reductase cluster in the more acid resistant strain ATCC 14579 were revealed. Furthermore, a major oxidative response was displayed, which included the induction of several oxidative stress related genes and the production of inactivation-associated reactive oxygen species (ROS), such as hydroxyl radicals, peroxynitrite, and superoxide. ROS were detected using fluorescent probes in combination with flow cytometry, including a newly developed method using a specific probe that enables superoxide detection in Grampositive and Gram-negative bacteria. The formation of ROS was also shown upon exposure to heat and was found to be oxygen dependant. Correspondingly, assessment of B. cereus stress survival capacity revealed increased heat- and acid-resistance with cells grown and exposed to stresses in the absence of oxygen. The excess ROS may originate from stressinduced dysfunction of the aerobic electron transfer chain, which was indicated by the induction of alternative electron transfer chain components upon exposure to organic and inorganic acid shocks. Upon exposure to stress, superoxide is generated through the premature leakage of electrons to oxygen at sites in the electron transfer chain at elevated rates. Subsequently, superoxide may promote the formation of other ROS, which can cause cellular damage leading to cell death. The induction of oxidative stress related genes has been reported in numerous other studies involving a wide range of bacteria exposed to different adverse conditions. However, a clear relation between the formation of ROS and the applied environmental stress was up to now not established. Secondary oxidative responses, including the formation of ROS, are possibly common bacterial responses to severe stresses under aerobic conditions. This thesis describes genomic differences between B. cereus strains and the acid stress response of these strains on transcriptome and phenotype levels, including measurements of intracellular ROS. The findings in this study can contribute to further understanding of bacterial stress responses and secondary oxidative responses. Furthermore, the results obtained may aid to optimize and select (combinations of) stresses to apply in hurdle technology, thus enabling design of safe, milder food processing and preservation techniques. <br/
Gene induction by ethanol stress in B. cereus ATCC 14579
No full textThe stress response of B. cereus ATCC 14579 is monitored true time, showing an enormous response in gene expression
Overexpression analysis of sigZ of B. cereus ATCC 14579.
No full textThe Bacillus cereus ATCC 14579 alternative σ factor σZ and its putative regulon have been characterized. σZ shows overall similarity with ECF σ factors and sigZ constitutes an operon together with asfZ encoding its putative anti-σ factor. Expression analysis revealed sigZ to be induced by an array of stresses, including exposure to ethanol, alkaline pH and heat shock, and a typical promoter binding site for the sigZ-operon was identified by 5’RACE. Phenotypic characterization of B. cereus ATCC 14579 and its sigZ-deletion strain revealed diminished growth performance and sporulation capacity. The σZ-regulon was successfully established by transcriptome analysis of a nisin inducible sigZ-overexpression strain. Overexpression of sigZ was shown to affect expression of 42 genes, including 33 genes encoding proteins located in the extracytoplasm. The identified σZ regulon contained genes encoding proteins situated in the extracytoplasm involved in cell surface modifications and transport. The regulation of genes encoding cell surface modification proteins implies σZ to be involved in the regulation of interaction of B. cereus ATCC 14579 with its environments, which includes human intestinal cells, possibly influencing its virulence status
Assessment of CcpA-mediated catabolite control of gene expression in ATCC 14579-2
No full textthe genome of ATCC 14579 in or in front of differently expressed genes between the deletion strain and the wild-type.<p><b>Copyright information:</b></p><p>Taken from "Assessment of CcpA-mediated catabolite control of gene expression in ATCC 14579"</p><p>http://www.biomedcentral.com/1471-2180/8/62</p><p>BMC Microbiology 2008;8():62-62.</p><p>Published online 16 Apr 2008</p><p>PMCID:PMC2358912.</p><p></p
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