Study on synthesizing of intracellular polysaccharide by Streptococcus mutans in dentinal tubules.

变形链球菌是一种致龋菌，由蔗糖合成水溶性葡聚糖(WSG)和水不溶性葡聚糖(WIG)，附着在牙齿上并增殖。本研究对具有comc、comX和scra基因缺陷的变形链球菌野生型菌株UA159及其基因敲除突变体进行了初步黏附、葡聚糖合成和侵袭牙本质小管的研究。所有突变株的水不溶性葡聚糖合成比例均低于野生型。在所有突变株中，牙本质切片上附着的水溶性葡聚糖比例也低于野生型。三种葡聚糖组分的总剂量在所有突变株中均有所下降。在脑心灌流培养24天时，comc和comX突变体的牙本质小管扩张率高于野生型。野生型和SCRA突变体的生长没有明显差异。在蔗糖存在下，SCRA突变体的WSG和WIG产量低于野生型。本研究表明，群体感应系统和PTS系统可能在葡聚糖合成、生物膜形成、胞内多糖的产生以及对牙本质小管的侵袭等过程中发挥重要作用。

Streptococcus mutans that is one of the cariogenic bacterium is synthesized the water-soluble glucan (WSG) and the water-insoluble glucan (WIG) from sucrose, adheres on the tooth, and proliferates. In this study, S. mutans wild-type strain UA159 and its knockout mutants, which were defective in comC, comX and scrA mutant, were examined for their ability for initial adhesion, glucan synthesis and invasion into dentinal tubles. The proportions of water-insoluble glucan synthesis in all mutant strains were less than the wild type. The proportions of water-soluble glucan adhering to dentin slices in all mutant strains were also less than in the wild type. The total dose of three kinds of glucan composition decreased in all mutant strains. The expansion rates of dentinal tubules by comC and comX mutant increased more than by the wild type when cultured in brain heart infusion for 24 days. There were no detectable difference in growth between wild-type and scrA-mutant. In the presence of sucrose, the produce of WSG and WIG in scrA-mutant was less than in wild-type. This study demonstrated that the quorum-sensing system and PTS system may play a crucial role in glucan synthesis, biofilm formation, production of intracellular-polysaccharide and invasion to dentinal tubules of S.mutans.