scholarly journals A Low pH-Inducible, PhoPQ-Dependent Acid Tolerance Response Protects Salmonella typhimurium against Inorganic Acid Stress

1998 ◽  
Vol 180 (9) ◽  
pp. 2409-2417 ◽  
Author(s):  
Bradley L. Bearson ◽  
Lee Wilson ◽  
John W. Foster
Keyword(s):  
Organic Acids ◽  
Salmonella Typhimurium ◽  
Organic Acid ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Low Ph ◽  
Inorganic Acid ◽  
Acid Tolerance Response ◽  
Acid Shock ◽  
Tolerance Response

ABSTRACT The acid tolerance response enables Salmonella typhimurium to survive exposures to potentially lethal acidic environments. The acid stress imposed in a typical assay for acid tolerance (log-phase cells in minimal glucose medium) was shown to comprise both inorganic (i.e., low pH) and organic acid components. A gene previously determined to affect acid tolerance, atbR, was identified as pgi, the gene encoding phosphoglucoisomerase. Mutations in pgi were shown to increase acid tolerance by preventing the synthesis of organic acids. Protocols designed to separate the stresses of inorganic from organic acids revealed that the regulators ς38 (RpoS), Fur, and Ada have major effects on tolerance to organic acid stress but only minor effects on inorganic acid stress. In contrast, the two-component regulatory system PhoP (identified as acid shock protein ASP29) and PhoQ proved to be important for tolerance to organic acid stress but had little effect against organic acid stress. PhoP mutants also failed to induce four ASPs, confirming a role for this regulator in acid tolerance. Acid shock induction of PhoP appears to occur at the transcriptional level and requires the PhoPQ system. Furthermore, induction by acid occurs even in the presence of high concentrations of magnesium, the ion known to be sensed by PhoQ. These results suggest that PhoQ can sense both Mg2+ and pH. SincephoP mutants are avirulent, the low pH activation of this system has important implications concerning the pathogenesis ofS. typhimurium. The involvement of four regulators, two of which are implicated in virulence, underscores the complexity of the acid tolerance stress response and further suggests that features of acid tolerance and virulence are interwoven.

scholarly journals The ToxR-Mediated Organic Acid Tolerance Response of Vibrio cholerae Requires OmpU

2001 ◽  
Vol 183 (9) ◽  
pp. 2746-2754 ◽  
Author(s):  
D. Scott Merrell ◽  
Camella Bailey ◽  
James B. Kaper ◽  
Andrew Camilli
Keyword(s):  
Stress Response ◽  
Organic Acid ◽  
Vibrio Cholerae ◽  
Ectopic Expression ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Independent Manner ◽  
Two Dimensional Gel Electrophoresis ◽  
Acid Tolerance Response ◽  
Tolerance Response

ABSTRACT It was previously demonstrated that the intestinal pathogenVibrio cholerae could undergo an adaptive stress response known as the acid tolerance response (ATR). The ATR is subdivided into two branches, inorganic ATR and organic ATR. The transcriptional regulator ToxR, while not involved in inorganic ATR, is required for organic ATR in a ToxT-independent manner. Herein, we investigate the effect of organic acid stress on global protein synthesis in V. cholerae and show by two-dimensional gel electrophoresis that the stress response alters the expression of more than 100 polypeptide species. The expression of more than 20 polypeptide species is altered in a toxR strain compared to the wild type. Despite this, ectopic expression of the porin OmpU from an inducible promoter is shown to be sufficient to bypass the toxR organic ATR defect. Characterization of the effect of organic acid stress onompU and ompT transcription reveals that whileompU transcription remains virtually unaffected,ompT transcription is repressed in a ToxR-independent manner. These transcript levels are similarly reflected in the extent of accumulation of OmpU and OmpT. Possible roles for OmpU in organic acid resistance are discussed.

scholarly journals The acid tolerance response of Salmonella typhimurium provides protection against organic acids

Microbiology ◽  
1996 ◽  
Vol 142 (11) ◽  
pp. 3195-3200 ◽  
Author(s):  
H. S. Baik ◽  
S. Bearson ◽  
S. Dunbar ◽  
J. W. Foster
Keyword(s):  
Organic Acids ◽  
Salmonella Typhimurium ◽  
Acid Tolerance ◽  
Acid Tolerance Response ◽  
Tolerance Response

High-Salt Preadaptation of Vibrio parahaemolyticus Enhances Survival in Response to Lethal Environmental Stresses

2014 ◽  
Vol 77 (2) ◽  
pp. 246-253 ◽  
Author(s):  
SAI SIDDARTH KALBURGE ◽  
W. BRIAN WHITAKER ◽  
E. FIDELMA BOYD
Keyword(s):  
Stress Response ◽  
Marine Environment ◽  
Vibrio Parahaemolyticus ◽  
High Salinity ◽  
Acid Stress ◽  
Acid Tolerance ◽  
High Salt ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
Tolerance Response

Adaptation to changing environmental conditions is an important strategy for survival of foodborne bacterial pathogens. Vibrio parahaemolyticus is a gram-negative seafoodborne enteric pathogen found in the marine environment both free living and associated with oysters. This pathogen is a moderate halophile, with optimal growth at 3% NaCl. Among the several stresses imposed upon enteric bacteria, acid stress is perhaps one of the most important. V. parahaemolyticus has a lysine decarboxylase system responsible for decarboxylation of lysine to the basic product cadaverine, an important acid stress response system in bacteria. Preadaptation to mild acid conditions, i.e., the acid tolerance response, enhances survival under lethal acid conditions. Because of the variety of conditions encountered by V. parahaemolyticus in the marine environment and in oyster postharvest facilities, we examined the nature of the V. parahaemolyticus acid tolerance response under high-salinity conditions. Short preadaptation to a 6% salt concentration increased survival of the wild-type strain but not that of a cadA mutant under lethal acid conditions. However, prolonged exposure to high salinity (16 h) increased survival of both the wild-type and the cadA mutant strains. This phenotype was not dependent on the stress response sigma factor RpoS. Although this preadaptation response is much more pronounced in V. parahaemolyticus, this characteristic is not limited to this species. Both Vibrio cholerae and Vibrio vulnificus also survive better under lethal acid stress conditions when preadapted to high-salinity conditions. High salt both protected the organism against acid stress and increased survival under −20°C cold stress conditions. High-salt adaptation of V. parahaemolyticus strains significantly increases survival under environmental stresses that would otherwise be lethal to these bacteria.

Comparative Analysis of Acid Resistance between Susceptible and Multi-Antimicrobial-Resistant Salmonella Strains Cultured under Stationary-Phase Acid Tolerance–Inducing and Noninducing Conditions

2003 ◽  
Vol 66 (5) ◽  
pp. 732-740 ◽  
Author(s):  
R. T. BACON ◽  
J. N. SOFOS ◽  
P. A. KENDALL ◽  
K. E. BELK ◽  
G. C. SMITH
Keyword(s):  
Stationary Phase ◽  
Antimicrobial Agents ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Low Ph ◽  
Acid Exposure ◽  
Acid Adaptation ◽  
Acid Shock ◽  
Resistant Strains

This study compared acid resistance levels among five antimicrobial-susceptible strains of Salmonella and five strains that were simultaneously resistant to a minimum of six antimicrobial agents. The induction of a stationary-phase acid tolerance response (ATR) was attempted by both transient low-pH acid shock and acid adaptation. For acid shock induction, strains were grown for 18 h in minimal E medium containing 0.4% glucose (EG medium) and exposed to sublethal acid stress (pH 4.3) for 2 h, and subsequently, both shocked and nonshocked cultures were acid challenged (pH 3.0) for 4 h. Acid adaptation was achieved by growing strains for 18 h in tryptic soy broth containing 1.0% glucose (TSB+G), while nonadapted cultures were grown for 18 h in glucose-free tryptic soy broth (TSB−G). Acid-adapted and nonadapted inocula were acid challenged (pH 2.3) for 4 h. Initial (0 h) mean populations of nonchallenged Salmonella were 8.5 to 8.7, 8.4 to 8.8, and 8.2 to 8.3 log CFU/ml for strains grown in EG medium, TSB−G, and TSB+G, respectively. After 4 h of acid challenge, mean populations were 3.0 to 4.8 and 2.5 to 3.7 log CFU/ml for previously acid-shocked susceptible and resistant strains, respectively, while corresponding counts for nonshocked strains were 4.3 to 5.5 log CFU/ml and 3.9 to 4.9 log CFU/ml. Following 4 h of acid exposure, acid-adapted cultures of susceptible and resistant strains had mean populations of 6.1 to 6.4 log CFU/ml and 6.4 to 6.6 log CFU/ml, respectively, while corresponding counts for nonadapted cultures were 1.9 to 2.1 log CFU/ml and 1.8 to 2.0 log CFU/ml, respectively. A low-pH–inducible ATR was not achieved through transient acid shock, while an ATR was evident following acid adaptation, as adapted populations were 4.2 to 4.8 log units larger than nonadapted populations following acid exposure. Although some strain-dependent variations in acid resistance were observed, results from this study suggest no association between susceptibility to antimicrobial agents and the ability of the Salmonella strains evaluated to survive low-pH stress.

Arginine and lysine decarboxylases and the Acid Tolerance Response of Salmonella Typhimurium

2010 ◽  
Vol 136 (3) ◽  
pp. 278-282 ◽  
Author(s):  
Avelino Álvarez-Ordóñez ◽  
Ana Fernández ◽  
Ana Bernardo ◽  
Mercedes López
Keyword(s):  
Salmonella Typhimurium ◽  
Acid Tolerance ◽  
Acid Tolerance Response ◽  
Tolerance Response
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