Document Detail

Role of Listeria monocytogenes sigma(B) in survival of lethal acidic conditions and in the acquired acid tolerance response.
MedLine Citation:
PMID:  12732538     Owner:  NLM     Status:  MEDLINE    
The food-borne pathogen Listeria monocytogenes can acquire enhanced resistance to lethal acid conditions through multiple mechanisms. We investigated contributions of the stress-responsive alternative sigma factor, sigma(B), which is encoded by sigB, to growth phase-dependent acid resistance (AR) and to the adaptive acid tolerance response in L. monocytogenes. At various points throughout growth, we compared the relative survival of L. monocytogenes wild-type and DeltasigB strains that had been exposed to either brain heart infusion (pH 2.5) or synthetic gastric fluid (pH 2.5) with and without prior acid adaptation. Under these conditions, survival of the DeltasigB strain was consistently lower than that of the wild-type strain throughout all phases of growth, ranging from 4 orders of magnitude less in mid-log phase to 2 orders of magnitude less in stationary phase. Survival of both DeltasigB and wild-type L. monocytogenes strains increased by 6 orders of magnitude upon entry into stationary phase, demonstrating that the L. monocytogenes growth phase-dependent AR mechanism is sigma(B) independent. sigma(B)-mediated contributions to acquired acid tolerance appear to be greatest in early logarithmic growth. Loss of a functional sigma(B) reduced the survival of L. monocytogenes at pH 2.5 to a greater extent in the presence of organic acid (100 mM acetic acid) than in the presence of inorganic acid alone (HCl), suggesting that L. monocytogenes protection against organic and inorganic acid may be mediated through different mechanisms. sigma(B) does not appear to contribute to pH(i) homeostasis through regulation of net proton movement across the cell membrane or by regulation of pH(i) buffering by the GAD system under the conditions examined in this study. In summary, a functional sigma(B) protein is necessary for full resistance of L. monocytogenes to lethal acid treatments.
Adriana Ferreira; David Sue; Conor P O'Byrne; Kathryn J Boor
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  69     ISSN:  0099-2240     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2003 May 
Date Detail:
Created Date:  2003-05-06     Completed Date:  2003-08-05     Revised Date:  2013-04-18    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2692-8     Citation Subset:  IM    
Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
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MeSH Terms
Adaptation, Physiological
Artificial Gene Fusion
Bacterial Proteins / genetics,  physiology*
Foodborne Diseases / etiology
Gastric Juice / microbiology
Genes, Bacterial
Glutamate Decarboxylase / metabolism
Hydrogen-Ion Concentration
Listeria monocytogenes / genetics,  growth & development,  pathogenicity,  physiology*
Listeriosis / etiology
Sigma Factor / genetics,  physiology*
Reg. No./Substance:
0/Acids; 0/Bacterial Proteins; 0/Protons; 0/SigB protein, Bacteria; 0/Sigma Factor; EC Decarboxylase

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