Document Detail

Cytoplasmic pH response to acid stress in individual cells of Escherichia coli and Bacillus subtilis observed by fluorescence ratio imaging microscopy.
MedLine Citation:
PMID:  22427503     Owner:  NLM     Status:  MEDLINE    
The ability of Escherichia coli and Bacillus subtilis to regulate their cytoplasmic pH is well studied in cell suspensions but is poorly understood in individual adherent cells and biofilms. We observed the cytoplasmic pH of individual cells using ratiometric pHluorin. A standard curve equating the fluorescence ratio with pH was obtained by perfusion at a range of external pH 5.0 to 9.0, with uncouplers that collapse the transmembrane pH difference. Adherent cells were acid stressed by switching the perfusion medium from pH 7.5 to pH 5.5. The E. coli cytoplasmic pH fell to a value that varied among individual cells (range of pH 6.2 to 6.8), but a majority of cells recovered (to pH 7.0 to 7.5) within 2 min. In an E. coli biofilm, cells shifted from pH 7.5 to pH 5.5 failed to recover cytoplasmic pH. Following a smaller shift (from pH 7.5 to pH 6.0), most biofilm cells recovered fully, although the pH decreased further than that of isolated adherent cells, and recovery took longer (7 min or longer). Some biofilm cells began to recover pH and then failed, a response not seen in isolated cells. B. subtilis cells were acid shifted from pH 7.5 to pH 6.0. In B. subtilis, unlike the case with E. coli, cytoplasmic pH showed no "overshoot" but fell to a level that was maintained. This level of cytoplasmic pH post-acid shift varied among individual B. subtilis cells (range of pH, 7.0 to 7.7). Overall, the cytoplasmic pHs of individual bacteria show important variation in the acid stress response, including novel responses in biofilms.
Keith A Martinez; Ryan D Kitko; J Patrick Mershon; Haley E Adcox; Kotiba A Malek; Melanie B Berkmen; Joan L Slonczewski
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-03-16
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  78     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-04-26     Completed Date:  2012-08-15     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3706-14     Citation Subset:  IM    
Department of Biology, Kenyon College, Gambier, Ohio, USA.
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MeSH Terms
Acids / metabolism,  toxicity*
Bacillus subtilis / chemistry,  metabolism,  physiology*
Biofilms / growth & development
Cytoplasm / chemistry*
Escherichia coli / chemistry,  metabolism,  physiology*
Hydrogen-Ion Concentration
Stress, Physiological*
Reg. No./Substance:

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