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Correia, Frederick F.,Lamont, Richard,Bayer, Manfred E.,Rosan, Burton,Dirienzo, Joseph M. Korean Academy of Oral Biology and the UCLA Dental 1997 International Journal of Oral Biology Vol.22 No.4
Streptococcus crista displays polar tufts of fimbriae through which it binds to Fusobacterium nucleatum to form morphological units termed "corncobs". In a previous report (Oral Microbiol. Immunol. 10: 220-226, 1995) Tn916 was used to make binding-deficient mutants of S. crista. In this study the transposon insertion site in one of these mutants, CC5A-B15, was characterized. Electron microscopy showed that the morphology of the fimbrial tufts of the binding-deficient mutant was altered. Genetic linkage between the Tn916 insertion in CC5A-B15 and the binding deficient phenotype was confirmed by back-crossing the mutated locus into the parental strain. The mutated locus was cloned and sequenced using an inverse polymerase chain reaction protocol. The resulting product was then used to obtain the wild type locus from a bacteriophage λEMBL3-CC5A and DNA library. The exact site of the Tn916 insertion was determined by comparison of the mutated and wild-type DNA sequences. Based on comparisons to Streptococcus pyogenes M1 and Escherichia coli K12 genome sequences, the transposable element disrupted an apparent ATP-binding cassette (ABC). This ABC transport locus consists of four open reading frames potentially encoding an ATP-binding protein, a lipoprotein, and two transport-related proteins. The results suggest that the reduction in binding of the S. crista mutant to F. nucleatum may be due to the altered transport and assembly of components of the fimbrial tufts.
Correia, F.F.,Waterbury, T.L.,Rosan, B.,DiRienzo, J.M. Korean Academy of Oral Biology and the UCLA Dental 2001 International Journal of Oral Biology Vol.26 No.1
The major outer membrane porin, FomA, from Fusobacterium mucleatum ATCC 10953 was previously shown to be a coaggregation receptor for Streptococcus crista CC5A. The fomA gene was amplified by PCR and cloned in Escherichia coli. The nucleotide sequence of the recombinant gene contained a three base pair deletion and four single base differences compared to the native fomA sequence. The recombinant gene product was glutathione-S-transferase (GST). The GST portion was removed by treatment with thrombin and the FomA portion purified in milligram quantities. The purified recombinant protein contained a glycylserine dipeptide at its amino terminus, bound IgG from antiserum made against native FomA, and retained the heat-modifiable property of the native protein. However, the recombinant FomA failed to bind to S. crista CC5A or inhibit coaggregation between this bacterium and F. nucleatum. FomA may require outer membrane components, such as lipopolysaccharide, to stabilize the protein in a structure recognized by the streptococcal adhesin.