ABSTRACT
A cosmid gene library of Actinomyces viscosus T14V was prepared in Escherichia coli to examine the expression of A. viscosus antigens and to gain insight into the structure of A. viscosus type 1 and type 2 fimbriae. Out of this library of 550 clones, 28 reacted in a colony immunoassay with antibodies against A. viscosus cells. The proteins responsible for these reactions were identified in three clones. Clones AV1209 and AV2009 displayed nonfimbrial antigens with subunits of 40 and 58 kilodaltons, respectively. Clone AV1402 showed a 59-kilodalton protein that reacted with monospecific antibody against type 2 fimbriae and that comigrated with a subunit of type 2 fimbriae during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This indicates that AV1402 expresses a gene (fimA) for a subunit of A. viscosus type 2 fimbriae.
Subject(s)
Actinomyces/genetics , Antigens, Bacterial/analysis , Cloning, Molecular , Escherichia coli/genetics , Fimbriae, Bacterial , Genes , Actinomyces/immunologyABSTRACT
A more sensitive test agar was developed to detect oral microbes with relatively low dextranase activity and to identify dextranase-negative mutants. Several oral streptococci that had previously been scored as dextranase negative readily decolorized the new, blue dextran-containing medium. To assess whether dextranase plays a role in glucan synthesis by oral streptococci, various glucan synthesis-defective mutants were tested for dextranase activity on the new medium. Mutants 4 and 27, which do not cause smooth-surface caries and which synthesize more soluble glucan than their parent, Streptococcus mutans 6715-13, were markedly deficient in these dextranase activity tests.
