甘露聚糖底物中共培养干酪乳杆菌与副干酪乳杆菌共生关系研究

Mutualism plays important role in evolution. Mutualistic interactions between lactic acid bacteria widely existed and varied in types. This mutualistic interactions are complicated, non-genus or species specific and depend on the contact level. Bacteriocin secreted by lactic acid bacteria are under regulation of quorum sensing and critical metabolites for inter-species communication. This research focuses on mutual effects of metabolism and dynamic transition of mutualism of lactic acid bacteria. This research constructs a co-culture model of two Lactobacillus strains, L. casei HDS-01and L. paracasei HD1.7 with mannans substrate. The substrate conversion and metabolic flow will be investigated at two contact level, i.e. cell-cell contact and cell-cell non-contact. The key metabolic pathway is the synthesis of L. casei mannanase and L. paracasei bacteriocin. The results will elaborate the interspecies mechanism of metabolic interaction. This research will (1) expand L. casei’s substrate types, improve the knowledge on intra-genus quorum sensing and effect of L. paracasei bacteriocin, (2) facilitate the identification of key genes in ecological adaption as well as the understanding of lactic acid bacteria co-evolution. The co-culture containing probiotics and prebiotics will render industrial significance in preparation and exploration of synbiotics.

共生是生物进化的重要机制。乳酸菌共生现象普遍，关系类型多样，彼此间复杂的相互作用无种属特异性且依赖接触方式。细菌素生成受群体感应调控，是乳酸菌种间交流的关键代谢物。本研究关注乳酸菌的代谢互作和共生关系的动态转化，以甘露聚糖为底物，构建干酪乳杆菌（Lactobacillus casei）和副干酪乳杆菌（L. paracasei）共培养模型。以细胞接触与非接触两种种方式，重点研究L. casei甘露聚糖酶产生和L. paracasei细菌素生成代谢路径，从营养、生物量、代谢物、甘露聚糖酶及群体感应相关基因表达水平，阐释共生关系类型与代谢互作方式。研究成果将扩展对L. casei底物范围的认识，填补L. paracasei细菌素属内种间群体感应调控机制的空白；有助于生态适应关键基因鉴定和乳酸菌协同进化的理解；共培养物在合生元制备开发中具有工业意义。

本项目以分离自酸菜发酵液的两株乳杆菌属（Lactobacillus）LAB干酪乳杆菌（Lactobacillus casei）HDS-01和副干酪乳杆菌（Lactobacillus paracasei）HD1.7为供试菌株，以L. casei HDS-01受聚糖类底物诱导产甘露聚糖酶和L. paracasei HD1.7受群体感应调控生成细菌素这两个特有代谢特性为切入点，构建两菌株共培养模型。以单培养为对照，分别从特有基因及其转录、生物量、代谢物和底物降解水平研究二者的代谢互作。研究成果有助于加深对Lactobacillus种间生态学关系和协同进化的理解；共培养混合物中同时含有益生菌、细菌素及甘露低聚糖，也为益生菌剂及合生元制备和开发提供了素材，具有一定的实践意义。L. casei HDS-01与L. paracasei HD1.7在魔芋粉底物中共培养时，甘露聚糖酶活力有所下降，糖代谢基因2941表达量变化不显著；细菌素效价降低，群体感应和细菌素生成基因的表达受到抑制。由于存在营养竞争，L. casei HDS-01与L. paracasei HD1.7共培养时，L. casei HDS-01产甘露聚糖酶的代谢通路正常，生物量、代谢物水平差异并不显著；L. paracasei HD1.7产细菌素的代谢通路受到抑制，生物量、代谢物水平差异显著低于单培养时。L. paracasei HD1.7在共培养中处于营养竞争的劣势地位，细菌密度低，显著抑制细菌素生成。而L. casei HDS-01在共培养中处于营养竞争的优势地位，共培养对甘露聚糖酶生成影响不大。