Microbiology of periodontal disease in Singapore and the discovery of a bacterial intron in Actinobacillus actinomycetemcomitans

Abstract

Ethnicity is a risk factor for periodontal disease. The occurrence of major periodontal pathogens in a total of 410 periodontally healthy and diseased subjects in the ethnic Chinese in Singapore were determined. Actinobacillus actinomycetemcomitans cdt; Porphyromonas gingivalis prtC and Tannerella forsythensis (Bacteroides forsythus) prtH genotypes correlated well with the periodontal status of the local population. A. actinomycetemcomitans possesses the cytolethal-distending toxin (CDT). The 2.1 kb cdt gene gave three reverse transcription-polymerase chain reaction (RT-PCR) bands of 2.1 kb, 1.5 kb and 0.9 kb. Recombinant E. coli possessing the cdt gene gave similar results. In vitro transcribed cdt RNA catalyzed its own excision. The spliced products possessed different 5a?? exons but shared the same 3a?? exon with ribosome-binding site present upstream. Conservation of splice-site consensus sequence was important for accurate splicing. The a??catalytic corea?? was a 0.56 kb RNA segment located within the 2.1 kb precursor RNA, capable of splicing heterologous RNA in the cis and trans configuration.