Amended Description of the Genes for Synthesis of Actinomyces naeslundii T14V Type 1 Fimbriae and Associated Adhesin
ARMY INST OF SURGICAL RESEARCH FORT SAM HOUSTON TX
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Studies of the prominent oral microorganism Actinomyces naeslundii have provided important insights into both the properties of fimbriae or pili on gram-positive bacteria 16, 18 and the underlying mechanisms of dental plaque formation 4. The fimbriae of A. naeslundii , which were among the first observed for a gram-positive species 11, consist of two functionally distinct types 5. The type 1 fimbriae mediate adhe- sion of this species to the tooth surface through the binding of adsorbed salivary proline-rich proteins PRPs 7, 10, 13, whereas the type 2 fimbriae promote biofilm formation 14 through recognition of hostlike saccharide motifs in the surface polysaccharides of early colonizing streptococci 3. The major subunits of type 1 and type 2 fimbriae, encoded by the genes fimP 19 and fimA 20, respectively, are similar in size 56 kDa and have sequences that are approximately 40 identical. The gene fimA of A. naeslundii T14V occurs between open reading frame 977 ORF 977, which may encode the type 2 fimbria-associated adhesin 12, and ORF 365 for a sortase that is required for the covalent polymerization of FimA monomers 20. In contrast, fimP of this strain appears to be flanked by three essential upstream ORFs i.e., ORF3-ORF2-ORF1 of unknown function and two essential downstream ORFs i.e., ORF4-ORF5 22, which include the partial coding sequence of a putative sortase 9. Moreover, the genes that reportedly flank fimP in strain T14V differ dramatically from those that flank this gene in type 1-fimbriated Actinomyces viscosus 19246 13.
- Genetic Engineering and Molecular Biology
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