Abstract
Aggregatibacter actinomycetemcomitans is an important pathogen related to aggressively progressive periodontal breakdown in adolescents and adults. The bacterium forms a tenacious biofilm on solid surfaces is important in colonization of the oral cavity. The genes of tight adherence (tad) locus reside in a 12-kb flp operon that contains 14 genes, flp-1-flp-2-tadV-rcpCAB-tadZABCDEFG. The purpose of this study was to sequence the tad locus in a highly aggregative and adherent A. actinomycetemcomitans serotype g designated NUM-Aa 4039 strain. The tad locus of NUM-Aa 4039 strain contained 14 genes in 11,559-bp nucleotides. The similarity of the tad locus sequence was 96.5% compared with that of the well-documented, rough, adherent strain CU1000. Almost all genes were similar to the CU1000 strains. However, the flp-1 and tadG genes of NUM-Aa 4039 showed 84.0% and 71.8% homology in their amino acid sequences compared to those of CU1000, respectively. The Flp1 major pilin protein of NUM-Aa 4039 consisted of 75 amino acids and several amino acid substitutions occurred in the C-terminus of the protein. It was classified as flp-1 allelic class type 6. The sequence variations of flp-1 and tadG genes may be due to the tight adherence and aggregation of NUM-Aa 4039.
