Stringent response and programed cell death mechanism of periodontal pathogenic bacteria

点击翻译按钮获取中文摘要

Porphyromonas gingivalis is a putative major etiology agent of adult periodontitis. It is suppose that P. gingivalis may survive in the oral biofilm. However, P. gingivalis quickly autolyzes in the culture media. To examine the molecular components of the P gingivalis autolysate, two-dimensional gel electrophoresis was performed. Many protein spots varied both in number and volume. One of these spots included Rgp as determined by N-terminal amino acid sequencing. Mutant of N-acetylmuramoyl-L-alanine amidase like protein gene of P. gingivalis was constructed by alleic exchange. Autolysis rate of the autolysin mutant was the same as that of parent strain. These results indicate that many autolysin may act the autolysis of P. gingivalis.From consideration that inside of oral biofilm may be innutritious space, mimic condition of oral biofilm was prepared by low concentration of THM medium. Major component of THM medium was Trypyone which is composed from peptide. P gingivalis could growth with metabolizing not amino acid but peptide. In low concentration of THM medium, autolysis rate of P gingivalis was decreased and living cells was increased. Proteome analysis of P. gingivalis cells in the low concentration of THM medium indicated that expression of many proteins decreased. It is considered that low concentration of THM medium is stringent state for P. gingivalis. One of the stringent response gene (relA/spot) mutant of P gingivalis decreased autolysis rate than parent strain. It was also observed that many protein expression were differ from relA/spot mutant and parent strain.These results suggest that high peptide concentration induce autolysis (programmed cell death) and low peptide concentration in vitro induce the stringent response gene expression, consequently autolysis rate of P. gingivalis turned slow. This mechanism may be possible to explain the survival of P. gingival in biofilm.