| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 101 === Streptococcus sanguinis is a member of the dental plaque and occasionally causes infective endocarditis. Thus far the gene cluster (pil) encoding type IV pili (Tfp) was found only in the genome of Streptococcus sanguinis SK36. Previous studies by using 5’ RACE analysis revealed 3 putative transcription initiation sites 5’ to the pil cluster. Short hair-like structures were observed on the surface of SK36 by using anti-SSA_2315 (PilA) antiserum under transmission electron microscopy. However, the biological functions of the Tfp in S. sanguinis SK36 remains unknown. This study aims to analyze the expression and function of the pil cluster. By using various pil promoter-reporter fusion strains, it was found that all 3 promoters were functional. The activity of a transcriptional fusion containing all 3 promoters was higher in the ccpA-deficient host than that in the wild-type background, indicating that the expression of the pil operon is subject to the regulation of CcpA. Western analysis of the PilA protein indicated that the biogenesis of Tfp was regulated by growth phases, with the highest expression at the early stationary phase. Inactivation of SSA_2313-2315 led to a 40% reduction in adherence to HeLa cells and squamous cell carcinoma (SCC-4) compared to the wild-type strain. Taken together, the expression of the pil cluster was regulated by a complex system and the biosynthesis of Tfp was closely associated with the development of growth phase. The binding of S. sanguinis SK36 Tfp to host cells supports the role of Tfp in the pathogenesis of S. sanguinis SK36.
|
|---|
