Acid stress in the food pathogen Bacillus cereus

Browne, Niall; Dowds, Barbara C. A.

doi:10.1046/j.1365-2672.2002.01541.x

Cited by 82 publications

(65 citation statements)

References 34 publications

(71 reference statements)

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“…Similar observations were also reported for Bacillus cereus, in which only one acid-sensitive single-knockout mutant was obtained despite screening of 1.7 ϫ 10 8 cells. Unfortunately, the identity of the mutated gene is not known (6). These and our own observations lead us to suggest that the genes that are responsible for long-term acid adaptation may have overlapping functions.…”

Section: Resultsmentioning

confidence: 90%

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Gene Expression Analysis of Corynebacterium glutamicum Subjected to Long-Term Lactic Acid Adaptation

et al. 2007

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Corynebacteria form an important part of the red smear cheese microbial surface consortium. To gain a better understanding of molecular adaptation due to low pH induced by lactose fermentation, the global gene expression profile of Corynebacterium glutamicum adapted to pH 5.7 with lactic acid under continuous growth in a chemostat was characterized by DNA microarray analysis. Expression of a total of 116 genes was increased and that of 90 genes was decreased compared to pH 7.5 without lactic acid, representing 7% of the genes in the genome. The up-regulated genes encode mainly transcriptional regulators, proteins responsible for export, import, and metabolism, and several proteins of unknown function. As much as 45% of the up-regulated open reading frames code for hypothetical proteins. These results were validated using real-time reverse transcription-PCR. To characterize the functions of 38 up-regulated genes, 36 single-crossover disruption mutants were generated and analyzed for their lactic acid sensitivities. However, only a sigB knockout mutant showed a highly significant negative effect on growth at low pH, suggesting a function in organic-acid adaptation. A sigE mutant already displayed growth retardation at neutral pH but grew better at acidic pH than the sigB mutant. The lack of acid-sensitive phenotypes in 34 out of 36 disrupted genes suggests either a considerable redundancy in acid adaptation response or coincidental effects. Other up-regulated genes included genes for ion transporters and metabolic pathways, including carbohydrate and respiratory metabolism. The enhanced expression of the nrd (ribonucleotide reductase) operon and a DNA ATPase repair protein implies a cellular response to combat acid-induced DNA damage. Surprisingly, multiple iron uptake systems (totaling 15% of the genes induced >2-fold) were induced at low pH. This induction was shown to be coincidental and could be attributed to iron-sequestering effects in complex media at low pH.

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Section: Resultsmentioning

confidence: 90%

“…At least the iron uptake systems are not protective per se. If the upregulated genes are indeed protective, one has to propose redundancy for these gene functions (6,14). Otherwise, upregulated genes might reflect a function in a slow-growth mode of the cell rather than in acid protection.…”

Section: Resultsmentioning

confidence: 99%

Gene Expression Analysis of Corynebacterium glutamicum Subjected to Long-Term Lactic Acid Adaptation

et al. 2007

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“…As in other gram-positive bacteria these proteins are under the control of the alternative sigma factor, B (52,70,71). Some investigations have also evaluated the response of B. cereus to acid, ethanol, and osmolarity, and the induction of several of the same proteins has been observed (13,52). However, to our knowledge, responses to bile (salts) have not been investigated in B. cereus, and this work describes the first in vitro global transcriptional response to bile salts in this group of bacteria.…”

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confidence: 99%

Low Concentrations of Bile Salts Induce Stress Responses and Reduce Motility inBacillus cereusATCC 14570

et al. 2007

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Tolerance to bile salts was investigated in forty Bacillus cereus strains, including 17 environmental isolates, 11 dairy isolates, 3 isolates from food poisoning outbreaks, and 9 other clinical isolates. Growth of all strains was observed at low bile salt concentrations, but no growth was observed on LB agar plates containing more than 0.005% bile salts. Preincubation of the B. cereus type strain, ATCC 14579, in low levels of bile salts did not increase tolerance levels. B. cereus ATCC 14579 was grown to mid-exponential growth phase and shifted to medium containing bile salts (0.005%). Global expression patterns were determined by hybridization of total cDNA to a 70-mer oligonucleotide microarray. A general stress response and a specific response to bile salts were observed. The general response was similar to that observed in cultures grown in the absence of bile salts but at a higher (twofold) cell density. Up-regulation of several putative multidrug exporters and transcriptional regulators and down-regulation of most motility genes were observed as part of the specific response. Motility experiments in soft agar showed that motility decreased following bile salts exposure, in accordance with the transcriptional data. Genes encoding putative virulence factors were either unaffected or down-regulated.

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“…An acidsensitive mutant appeared to suffer from membrane damage that appeared to affect ability of the strain to control its internal pH (24). This mutant underexpresses a number of proteins.…”

Section: Bacillus Cereusmentioning

confidence: 99%

Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

Cotter

Hill

2003

Microbiol Mol Biol Rev

1,002

828

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Gram-positive bacteria possess a myriad of acid resistance systems that can help them to overcome the challenge posed by different acidic environments. In this review the most common mechanisms are described: i.e., the use of proton pumps, the protection or repair of macromolecules, cell membrane changes, production of alkali, induction of pathways by transcriptional regulators, alteration of metabolism, and the role of cell density and cell signaling. We also discuss the reponses of Listeria monocytogenes, Rhodococcus, Mycobacterium, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus, oral streptococci, and lactic acid bacteria to acidic environments and outline ways in which this knowledge has been or may be used to either aid or prevent bacterial survival in low-pH environments

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Acid stress in the food pathogen Bacillus cereus

Abstract: The work has implications for the processing of B. cereus-associated foods by acidification. The linked developmental processes of stationary phase, sporulation and possibly competence appear to be involved in the response to acid stress.

Cited by 82 publications

References 34 publications

Gene Expression Analysis of Corynebacterium glutamicum Subjected to Long-Term Lactic Acid Adaptation

Gene Expression Analysis of Corynebacterium glutamicum Subjected to Long-Term Lactic Acid Adaptation

Low Concentrations of Bile Salts Induce Stress Responses and Reduce Motility inBacillus cereusATCC 14570

Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

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