Unknown,Transcriptomics,Genomics,Proteomics

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Physiological and transcriptional response of Lactobacillus casei ATCC 334 to acid stress

ABSTRACT: This study investigated features of the acid tolerance response (ATR) in Lactobacillus casei ATCC 334. To optimize ATR induction, cells were acid adapted for 10 or 20 min at different pH values (range, 3.0 to 5.0) and then acid challenged at pH 2.0. Adaptation over a broad range of pHs improved acid tolerance, but the highest survival was noted in cells acid adapted for 10 or 20 min at pH 4.5. Analysis of cytoplasmic membrane fatty acids (CMFAs) in acid-adapted cells showed that they had significantly (P < 0.05) higher total percentages of saturated and cyclopropane fatty acids than did control cells. Specifically, large increases in the percentages of C(14:0), C(16:1n(9)), C(16:0), and C(19:0(11c)) were noted in the CMFAs of acid-adapted and acid-adapted, acid-challenged cells, while C(18:1n(9)) and C(18:1n(11)) showed the greatest decrease. Comparison of the transcriptome from control cells (grown at pH 6.0) against that from cells acid adapted for 20 min at pH 4.5 indicated that acid adaption invoked a stringent-type response that was accompanied by other functions which likely helped these cells resist acid damage, including malolactic fermentation and intracellular accumulation of His. Validation of microarray data was provided by experiments that showed that L. casei survival at pH 2.5 was improved at least 100-fold by chemical induction of the stringent response or by the addition of 30 mM malate or 30 mM histidine to the acid challenge medium. To our knowledge, this is the first report that intracellular histidine accumulation may be involved in bacterial acid resistance. This study includes 5 samples that were analyzed (this includes a control). Four replicates were done on the full experiment. The control was cells that received no acid treatment prior to RNA isolation

ORGANISM(S): Lactobacillus casei ATCC 334

SUBMITTER: Jeff Broadbent

PROVIDER: E-GEOD-22318 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Physiological and transcriptional response of Lactobacillus casei ATCC 334 to acid stress.

Broadbent Jeff R JR Larsen Rebecca L RL Deibel Virginia V Steele James L JL

Journal of bacteriology 20100305 9

This study investigated features of the acid tolerance response (ATR) in Lactobacillus casei ATCC 334. To optimize ATR induction, cells were acid adapted for 10 or 20 min at different pH values (range, 3.0 to 5.0) and then acid challenged at pH 2.0. Adaptation over a broad range of pHs improved acid tolerance, but the highest survival was noted in cells acid adapted for 10 or 20 min at pH 4.5. Analysis of cytoplasmic membrane fatty acids (CMFAs) in acid-adapted cells showed that they had signifi ...[more]

PMID: 20207759

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Project description:Reactive nitrogen species (RNS) derived from dietary and salivary inorganic nitrates (NO3-) foment innate host defenses associated with the acidity of the stomach. The mechanisms by which these reactive species exert antibiotic activity in the gastric lumen are, however, poorly understood. To identify targets of RNS, the genetically tractable acid tolerance response (ATR) that enables enteropathogens to survive the harsh acidity of the stomach was screened for signaling pathways responsive to RNS. The nitric oxide (NO) donor spermine NONOate derepressed the Fur regulon that controls secondary lines of resistance against organic acids. Despite inducing a Fur-mediated adaptive response, acidified RNS largely boosted gastric host defenses as demonstrated by the fact that Salmonella bacteria exposed to spermine NONOate during mildly acidic conditions were not only shed in low amounts in feces, but also exhibited ameliorated oral virulence. NO prevented Salmonella from mounting a de novo ATR, but was unable to suppress an already functional protective response, indicating that RNS target regulatory cascades but not the effectors that defend against the rigors of gastric acidity. Transcriptional and translational analyses revealed that the PhoPQ signaling cascade is a critical ATR target of NO in rapidly growing Salmonella. Inhibition of PhoPQ signaling appears to contribute to most of the NO-mediated abrogation of the ATR in log phase bacteria, because the augmented acid sensitivity of phoQ-deficient Salmonella was not further enhanced after RNS treatment. Since PhoPQ-regulated acid resistance is widespread in enteric pathogens, the RNS-mediated inhibition of the Salmonella ATR described herein may represent a common component of the innate host defenses of the gastric lumen. Keywords: acid tolerance response, nitric oxide Microarray analyses were conducted comparing transcript levels of log-phase Salmonella cultured in minimal E salts + 0.4% glucose, pH 4.4 in the presence or absence of 250 ÂµM spermine NONOate for 1 hour. Microarrays were performed in triplicate under identical conditions (3 biological replicates).

Dataset Information

Physiological and transcriptional response of Lactobacillus casei ATCC 334 to acid stress

Publications

Physiological and transcriptional response of Lactobacillus casei ATCC 334 to acid stress.

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