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Journal of Bacteriology, April 2000, p. 2299-2306, Vol. 182, No. 8
Department of Microbiology, University of
Minnesota Medical School,1 and
Department of Genetics, Cell Biology and Development,
University of Minnesota,2 Minneapolis, Minnesota
55455
Received 18 October 1999/Accepted 22 January 2000
Aggregation substance proteins encoded by the sex pheromone plasmid
family of Enterococcus faecalis have been shown previously to contribute to the formation of a stable mating complex between donor
and recipient cells and have been implicated in the virulence of this
increasingly important nosocomial pathogen. In an effort to
characterize the protein further, prgB, the gene encoding
the aggregation substance Asc10 on pCF10, was cloned in a vector
containing the nisin-inducible nisA promoter and its
two-component regulatory system. Expression of aggregation substance
after nisin addition to cultures of E. faecalis and the
heterologous bacteria Lactococcus lactis and
Streptococcus gordonii was demonstrated. Electron
microscopy revealed that Asc10 was presented on the cell surfaces of
E. faecalis and L. lactis but not on that of
S. gordonii. The protein was also found in the cell culture
supernatants of all three species. Characterization of Asc10 on the
cell surfaces of E. faecalis and L. lactis
revealed a significant increase in cell surface hydrophobicity upon
expression of the protein. Heterologous expression of Asc10 on L. lactis also allowed the recognition of its binding ligand (EBS)
on the enterococcal cell surface, as indicated by increased transfer of
a conjugative transposon. We also found that adhesion of
Asc10-expressing bacterial cells to fibrin was elevated, consistent
with a role for the protein in the pathogenesis of enterococcal
endocarditis. The data demonstrate that Asc10 expressed under the
control of the nisA promoter in heterologous species will
be an useful tool in the detailed characterization of this important
enterococcal conjugation protein and virulence factor.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Heterologous Inducible Expression of
Enterococcus faecalis pCF10 Aggregation Substance Asc10 in
Lactococcus lactis and Streptococcus
gordonii Contributes to Cell Hydrophobicity and Adhesion
to Fibrin
*
Corresponding author. Mailing address: Department of
Microbiology, University of Minnesota Medical School, Box 196 FUHC,
1460 Mayo Memorial Building, 420 Delaware St. S.E., Minneapolis, MN 55455. Phone: (612) 625-9930. Fax: (612) 626-0623. E-mail:
gary-d{at}biosci.cbs.umn.edu.
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