Affiliation:
1. Department of Medical Microbiology, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands
Abstract
ABSTRACT
Viridans group streptococci (VS) from the oral cavity entering the bloodstream may initiate infective endocarditis (IE). We aimed to identify genes expressed in response to a pH increase from slightly acidic (pH 6.2) to neutral (pH 7.3) as encountered by VS entering the bloodstream from the oral cavity. Using a recently developed promoter-screening vector, we isolated five promoter fragments from the genomic DNA of
Streptococcus gordonii
CH1 responding to this stimulus. No common regulatory sequences were identified in these promoter fragments that could account for the coordinate expression of the corresponding genes. One of the isolated fragments contained the promoter region and 5′ end of a gene highly homologous to the methionine sulfoxide reductase gene (
msrA
) of various bacterial and eukaryotic species. This gene has been found to be activated in
S. gordonii
strain V288 in a rabbit model of IE (A. O. Kiliç, M. C. Herzberg, M. W. Meyer, X. Zhao, and L. Tao, Plasmid 42:67–72, 1999). We isolated and characterized the
msrA
gene of
S. gordonii
CH1 and constructed a chromosomal insertion mutant. This mutant was more sensitive to hydrogen peroxide, suggesting a role for the streptococcal MsrA in protecting against oxidative stress. Moreover, MsrA appeared to be important for the growth of
S. gordonii
CH1 under aerobic and anaerobic conditions. Both these properties of MsrA may contribute to the ability of
S. gordonii
to cause IE.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
38 articles.
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