Comparison of characteristics important for survival in pork processing environments of Salmonella Typhimurium, S. Derby, S. Infantis and S. Brandenburg

Salmonella is the causative agent of salmonellosis. In general, salmoellae infections in humans are foodborne. In particular food products of animal origin are an important cause of salmonellosis. Epidemiological studies have sown that in Europe up to 15-20% of all human cases of salmonellosis wre associated with consumption of pork

Short- and Long-Term Biomarkers for Bacterial Robustness: A Framework for Quantifying Correlations between Cellular Indicators and Adaptive Behavior

The ability of microorganisms to adapt to changing environments challenges the prediction of their history-dependent behavior. Cellular biomarkers that are quantitatively correlated to stress adaptive behavior will facilitate our ability to predict the impact of these adaptive traits. Here, we present a framework for identifying cellular biomarkers for mild stress induced enhanced microbial robustness towards lethal stresses. Several candidate-biomarkers were selected by comparing the genome-wide transcriptome profiles of our model-organism Bacillus cereus upon exposure to four mild stress conditions (mild heat, acid, salt and oxidative stress). These candidate-biomarkers—a transcriptional regulator (activating general stress responses), enzymes (removing reactive oxygen species), and chaperones and proteases (maintaining protein quality)—were quantitatively determined at transcript, protein and/or activity level upon exposure to mild heat, acid, salt and oxidative stress for various time intervals. Both unstressed and mild stress treated cells were also exposed to lethal stress conditions (severe heat, acid and oxidative stress) to quantify the robustness advantage provided by mild stress pretreatment. To evaluate whether the candidate-biomarkers could predict the robustness enhancement towards lethal stress elicited by mild stress pretreatment, the biomarker responses upon mild stress treatment were correlated to mild stress induced robustness towards lethal stress. Both short- and long-term biomarkers could be identified of which their induction levels were correlated to mild stress induced enhanced robustness towards lethal heat, acid and/or oxidative stress, respectively, and are therefore predictive cellular indicators for mild stress induced enhanced robustness. The identified biomarkers are among the most consistently induced cellular components in stress responses and ubiquitous in biology, supporting extrapolation to other microorganisms than B. cereus. Our quantitative, systematic approach provides a framework to search for these biomarkers and to evaluate their predictive quality in order to select promising biomarkers that can serve to early detect and predict adaptive traits

Comparative analyses imply that the enigmatic sigma factor 54 is a central controller of the bacterial exterior

Contains fulltext : 95738.pdf (publisher's version ) (Open Access)BACKGROUND: Sigma-54 is a central regulator in many pathogenic bacteria and has been linked to a multitude of cellular processes like nitrogen assimilation and important functional traits such as motility, virulence, and biofilm formation. Until now it has remained obscure whether these phenomena and the control by Sigma-54 share an underlying theme. RESULTS: We have uncovered the commonality by performing a range of comparative genome analyses. A) The presence of Sigma-54 and its associated activators was determined for all sequenced prokaryotes. We observed a phylum-dependent distribution that is suggestive of an evolutionary relationship between Sigma-54 and lipopolysaccharide and flagellar biosynthesis. B) All Sigma-54 activators were identified and annotated. The relation with phosphotransfer-mediated signaling (TCS and PTS) and the transport and assimilation of carboxylates and nitrogen containing metabolites was substantiated. C) The function annotations, that were represented within the genomic context of all genes encoding Sigma-54, its activators and its promoters, were analyzed for intra-phylum representation and inter-phylum conservation. Promoters were localized using a straightforward scoring strategy that was formulated to identify similar motifs. We found clear highly-represented and conserved genetic associations with genes that concern the transport and biosynthesis of the metabolic intermediates of exopolysaccharides, flagella, lipids, lipopolysaccharides, lipoproteins and peptidoglycan. CONCLUSION: Our analyses directly implicate Sigma-54 as a central player in the control over the processes that involve the physical interaction of an organism with its environment like in the colonization of a host (virulence) or the formation of biofilm

Comparison of characteristics important for survival in pork processing environments of Salmonella Typhimurium, S. Derby, S. Infantis and S. Brandenburg

Salmonella is the causative agent of salmonellosis. In general, salmoellae infections in humans are foodborne. In particular food products of animal origin are an important cause of salmonellosis. Epidemiological studies have sown that in Europe up to 15-20% of all human cases of salmonellosis wre associated with consumption of pork.</p

Comparative transcriptome and phenotype analysis of acid-stressed Bacillus cereus strain ATCC 14579

The food-borne human pathogen Bacillus cereus is found in environments that often have a low pH, such as food and soil. The physiological response upon exposure to several levels of acidity were investigated of B. cereus model strain ATCC 14579, to elucidate the response of B. cereus to acid stress. pH 5.4, pH 5.0, pH 4.8 and pH 4.5 were selected to conduct microarray analyses, based on the differences in physiological response upon exposure to the acid conditions. The transcriptome data revealed response specific profiles. Showing mechanisms induced upon all the different acid down-shocks, such as nitrate reductase and energy production genes, and several genes specifically expressed differentially in mild or lethal levels of acidity, such as F1F0-ATPase and cydAB. Furthermore, mechanisms involved in oxidative stress response were found highly up-regulated in response to both mild and lethal acid stress. The induction of oxidative stress related genes may be a response to the formation of reactive oxygen species by a perturbation of the electron transport chain. Therefore, the formation of hydroxyl radicals and/ or peroxynitrite was monitored upon exposure to the different levels of acidity with a fluorescent probe in a flow cytometer. The formation of these oxidative compounds was shown to be specific for lethal pHs and a model to relate radical formation with the observed transcriptome profiles was proposed

Comparative transcriptome and phenotype analysis of acid-stressed Bacillus cereus strain ATCC 14579

The food-borne human pathogen Bacillus cereus is found in environments that often have a low pH, such as food and soil. The physiological response upon exposure to several levels of acidity were investigated of B. cereus model strain ATCC 14579, to elucidate the response of B. cereus to acid stress. pH 5.4, pH 5.0, pH 4.8 and pH 4.5 were selected to conduct microarray analyses, based on the differences in physiological response upon exposure to the acid conditions. The transcriptome data revealed response specific profiles. Showing mechanisms induced upon all the different acid down-shocks, such as nitrate reductase and energy production genes, and several genes specifically expressed differentially in mild or lethal levels of acidity, such as F1F0-ATPase and cydAB. Furthermore, mechanisms involved in oxidative stress response were found highly up-regulated in response to both mild and lethal acid stress. The induction of oxidative stress related genes may be a response to the formation of reactive oxygen species by a perturbation of the electron transport chain. Therefore, the formation of hydroxyl radicals and/ or peroxynitrite was monitored upon exposure to the different levels of acidity with a fluorescent probe in a flow cytometer. The formation of these oxidative compounds was shown to be specific for lethal pHs and a model to relate radical formation with the observed transcriptome profiles was proposed

Analysis of germination and outgrowth of sorbic acid-stressed Bacillus cereus ATCC 14579 spores.

Sorbic acid (SA) is widely used as a preservative, but the effect of SA on spore germination and outgrowth has gained limited attention up to now. Therefore, the effect of sorbic acid on germination of spores of B. cereus strain ATCC 14579 was analyzed both at phenotype and transcriptome level. Spore germination and outgrowth was assessed at pH 5.5 without and with 0.75, 1.5 and 3.0mM (final concentrations) undissociated sorbic acid (HSA). This resulted in distinct HSA concentration-dependent phenotypes, varying from delays in germination and outgrowth to complete blockage of germination at 3.0mM HSA. The phenotypes reflecting different stages in the germination process could be confirmed using flow cytometry and could be recognized at transcriptome level by distinct expression profiles. In the absence and presence of 0.75 and 1.5mM HSA, similar cellular ATP levels were found up to the initial stage of outgrowth, suggesting that HSA-induced inhibition of outgrowth is not caused by depletion of ATP. Transcriptome analysis revealed the presence of a limited number of transcripts in dormant spores, outgrowth related expression, and genes specifically associated with sorbic acid stress, including alterations in cell envelope and multi-drug resistance. The potential role of these HSA-stress associated genes in spore outgrowth is discussed

Comparative transcriptome and phenotype analysis of acid-stressed Bacillus cereus strain ATCC 10987

The food-borne human pathogen Bacillus cereus is found in environments that often have a low pH, such as food and soil. The physiological response upon exposure to several levels of acidity were investigated of B. cereus model strain ATCC 10987, to elucidate the response of B. cereus to acid stress. pH 5.4, pH 5.0, pH 4.8 and pH 4.5 were selected to conduct microarray analyses, based on the differences in physiological response upon exposure to the acid conditions. The transcriptome data revealed response specific profiles. Showing mechanisms induced upon all the different acid down-shocks, such as nitrate reductase and energy production genes, and several genes specifically expressed differentially in mild or lethal levels of acidity, such as F1F0-ATPase and cydAB. Furthermore, mechanisms involved in oxidative stress response were found highly up-regulated in response to both mild and lethal acid stress. The induction of oxidative stress related genes may be a response to the formation of reactive oxygen species by a perturbation of the electron transport chain. Therefore, the formation of hydroxyl radicals and/ or peroxynitrite was monitored upon exposure to the different levels of acidity with a fluorescent probe in a flow cytometer. The formation of these oxidative compounds was shown to be specific for lethal pHs and a model to relate radical formation with the observed transcriptome profiles was proposed