Document Detail

Mutation of the NADH oxidase gene (nox) reveals an overlap of the oxygen- and acid-mediated stress responses in Streptococcus mutans.
MedLine Citation:
PMID:  22179247     Owner:  NLM     Status:  MEDLINE    
NADH oxidase (Nox) is a flavin-containing enzyme used by Streptococcus mutans to reduce dissolved oxygen encountered during growth in the oral cavity. In this study, we characterized the role of the NADH oxidase in the oxidative and acid stress responses of S. mutans. A nox-defective mutant strain of S. mutans and its parental strain, the genomic type strain UA159, were exposed to various oxygen concentrations at pH values of 5 and 7 to better understand the adaptive mechanisms used by the organism to withstand environmental pressures. With the loss of nox, the activities of oxygen stress response enzymes such as superoxide dismutase and glutathione oxidoreductase were elevated compared to those in controls, resulting in a greater adaptation to oxygen stress. In contrast, the loss of nox led to a decreased ability to grow in a low-pH environment despite an increased resistance to severe acid challenge. Analysis of the membrane fatty acid composition revealed that for both the nox mutant and UA159 parent strain, growth in an oxygen-rich environment resulted in high proportions of unsaturated membrane fatty acids, independent of external pH. The data indicate that S. mutans membrane fatty acid composition is responsive to oxidative stress, as well as changes in environmental pH, as previously reported (E. M. Fozo and R. G. Quivey, Jr., Appl. Environ. Microbiol. 70:929-936, 2004). The heightened ability of the nox strain to survive acidic and oxidative environmental stress suggests a multifaceted response system that is partially dependent on oxygen metabolites.
Adam M Derr; Roberta C Faustoferri; Matthew J Betzenhauser; Kaisha Gonzalez; Robert E Marquis; Robert G Quivey
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2011-12-16
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  78     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-01-31     Completed Date:  2012-05-03     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:  1215-27     Citation Subset:  IM    
Center for Oral Biology and Department of Microbiology and Immunology, University of Rochester, Rochester, New York, USA.
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MeSH Terms
Acids / toxicity*
Cell Membrane / chemistry
Fatty Acids / analysis
Hydrogen-Ion Concentration
Microbial Viability / drug effects
Multienzyme Complexes / deficiency,  metabolism*
NADH, NADPH Oxidoreductases / deficiency,  metabolism*
Oxidative Stress
Oxygen / toxicity*
Streptococcus mutans / drug effects*,  enzymology,  physiology*
Stress, Physiological*
Grant Support
Reg. No./Substance:
0/Acids; 0/Fatty Acids; 0/Multienzyme Complexes; 7782-44-7/Oxygen; EC 1.6.-/NADH oxidase; EC 1.6.-/NADH, NADPH Oxidoreductases

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