Prevalence of the amylase-binding protein A gene (abpA) in oral streptococci

Salivary amylase binds specifically to a number of oral streptococcal speci es. This interaction may play an important role in dental plaque formation, Recently, a 585-bp gene was cloned and sequenced from Streptococcus gordon ii Challis encoding a 20.5-kDa amylase-binding protein (AbpA), The goal of this study was to determine if related genes are present in other species o f oral streptococci, Biotinylated abpA was used in Southern blot analysis t o screen genomic DNA from several strains representing eight species of ora l streptococci, This probe hybridized with a 4.0-kb HindIII restriction fra gment from all 13 strains of S, gordonii tested. The probe did not appear t o bind to any restriction fragments from other species of amylase-binding o ral streptococci including Streptococcus mitis (with the exception of 1 of 14 strains), Streptococcus crista (3 strains), Streptococcus anginosus (1 s train), and Streptococcus parasangruinis (1 strain), or to non-amylase-bind ing oral streptococci including Streptococcus sanguinis (3 strains), Strept ococcus oralis (4 strains), and Streptococcus mutans (1 strain). Primers ho mologous to sequences within the 3' and 5' ends of abpA yielded products of 400 bp following PCR of genomic DNA from the Southern blot-positive strain s. Several of these PCR products were cloned and sequenced, The levels of s imilarity of these cloned products to the abpA of S, gordonii Challis range d from 91 to 96%, These studies reveal that the abpA gene appears to be spe cific to S, gordonii and differs from genes encoding amylase-binding protei ns from other species of amylase-binding streptococci.