Development of probiotics which regulate bacterial quorum sensing

群体感应（Quorum sensing， QS）是一种根据细菌密度产生的自诱导剂（autoinducer， AI）对细菌基因进行调控的系统。细菌生物膜与免疫逃逸、抗微生物药物耐药性有关，其形成受QS的调控。为了开发调节细菌群体感应的益生菌，研究了肠道菌群对螺旋菌形成生物膜的影响。采用大肠杆菌建立了微孔板生物膜测定方法。在这个实验中，添加AI-2增加了大肠杆菌的生物膜形成。对16种25株肠道菌群进行了研究，结果表明：长双歧杆菌、艰难梭菌、粪肠球菌、干酪乳杆菌、解糖胃杆菌和小苗细孔菌的培养上清液对大肠杆菌的生物膜形成有抑制作用。相反，芽孢杆菌和坏死梭杆菌的培养上清液促进了生物膜的形成。由于幽门螺杆菌TK1402染色株与未产生AI-2的luxS突变株在生物膜形成方面无显著差异，推测QS未诱导IL幽门螺杆菌形成生物膜。利用从健康成人粪便中分离的576株细菌，研究了这些细菌的培养上清液对大肠杆菌形成生物膜的影响。12株对生物膜的抑制作用低于对照的80%。由于大肠杆菌不能有效形成生物膜，因此使用534个染色剂进行了额外的实验。43株和22株培养上清液对大肠杆菌生物膜形成的抑制作用分别大于20%和50%。42株和5株培养上清液对金黄色葡萄球菌生物膜形成的抑制作用分别大于5%和50%。这些菌株的鉴定以及这些菌株对粘附素和细菌毒素的qs相关基因表达的影响有待进一步研究。

Quorum sensing (QS) is a system for regulation of bacterial gene by autoinducer (AI) which is produced according to bacterial density. Bacterial biofilm is associated with immunological escape, resistance to anti-microbial agents, and its formation is regulated by QS. In order to develop the probiotics which regulate bacterial quorum sensing, the effect of intestinal flora bacteria on biofilm formation by E. coil was examined.Biofilm assay in microplate was established by using E. coll. Addition of AI-2 increased biofilm formation by E. coli in this assay. Using 16 species and 25 strains of intestinal flora bacteria, it was shown that culture supernatants of Bifidobacterium longm, Clostridium difficile, Enterococcus faecalis, Lactobacillus casei, Peptoniphilus asaccharolyticus and Veillonella parvula inhibited biofilm formation by E. coil. In contrast, culture supernatants of Bcateroides and Fusobacterium necrophorum enhanced biofilm formation. As there was no significant difference in biofilm formation between Helicobacter pylori TK1402 stain and its luxS mutant strain without AI-2 production, it was speculated that biofilm formation was not induced in IL pylori by QS.Using 576 strains isolated from feces of healthy adults, the effects of culture supernatants of these bacteria on biofilm formation by E. coli was examined. Twelve strains inhibited the biofilm formation with less than 80 % level of control. As biofilm formation by E. coli was not effectively done, the additional experiment using 534 stains was performed. Culture supernatants of 43 and 22 strains inhibited biofilm formation by E. coli by more than 20% and 50%, respectively. Culture supernatants of 42 and 5 strains inhibited biofilm formation by S. aureus by more than 205 and 50%, respectively. Identification of these strains and the effects of these stains on the expression of QS-related genes for adhesin and bacterial toxin need to be clarified.