基于细菌互作的蜡样芽孢杆菌调控彭泽鲫肠道菌群平衡及代谢功能机制的研究

Microbial interaction is the key for intestinal microbial community maintaining the dynamic homeostasis and completing the systematic level metabolism. The result of our study suggested that the Probiotics Bacillus cereus could significantly improve the health and growth performance of Pengze crucian carp (Carassius auratus var. Pengze), however, much less is known about the regulation mechanism of B. cereus regulating dynamic homeostasis and nutrition metabolism of intestinal microbiota. Through the feeding growth experiment, this project intends to study: 1) community succession of intestinal microbial community of Pengze crucian carp, and explore the interaction, topological roles of bacterial species and their impacts in the flora ecosystem by construction of intestinal bacterial ecological network model, in order to reveal the mechanism of B. cereus regulating the dynamic homeostasis of intestinal microbiota; 2) determine the metabolic function of different communities and their contribution at the species level, and then explore the interaction mechanism within bacterial metabolism combined with ecological network; 3) reflect system level metabolic activity of intestinal microbiota at level of transcriptional gene, and further explore the mechanism of bacteria metabolism completing the system level metabolism through specie-specie interaction by correlation analysis of species-genes; 4) explore the mechanism of B. cereus improving the metabolism of intestinal flora under the level of small molecule metabolites by the analysis of metabolites. The completion of the project, to a certain extent, would prove mechanism of B. cereus regulating dynamic homeostasis and improving nutrient metabolism of intestinal microbiota, and provide a theoretical basis for the rational use of probiotics in aquaculture.

细菌互作是肠道菌群维系其动态平衡及完成系统水平代谢功能的关键。申请人的前期研究发现，益生菌蜡样芽孢杆菌可显著改善彭泽鲫健康和生长性能，但其调控肠道菌群平衡及其营养代谢的具体作用机制尚不明确。本项目将通过摄食生长实验，拟研究：1）彭泽鲫肠道菌群的群落演替，并构建细菌生态网络模型以探究细菌物种的互作关系和拓扑角色及其在菌群生态系统中的作用，以揭示蜡样芽孢杆菌调节肠道菌群平衡的作用机制；2）在物种水平上确定不同菌群的代谢功能及其贡献度，结合生态网络，探究细菌间代谢互作的机制；3）宏转录基因水平上反映肠道细菌的系统水平代谢活动，通过物种-基因的一致性关联分析，进一步探究细菌代谢通过互作完成系统水平代谢功能的作用机制；4）基于代谢产物差异分析，在小分子代谢物水平探究蜡样芽孢杆菌改善肠道菌群代谢营养物质的机理。通过上述研究，一定程度上可揭示蜡样芽孢杆菌调节肠道菌群平衡及改善肠道细菌营养代谢的作用机制。

肠道菌群在宿主的营养代谢、免疫调节以及抑制病原菌入侵过程中承担着重要的角色，所以维持肠道菌群平衡对宿主的健康至关重要。益生菌可调节肠道菌群平衡，蜡样芽孢杆菌被证实可有效改善水产动物的健康和生长性能，但其具体作用机制尚不明确。本项目以彭泽鲫研究对象，基于生长、消化、肉质和肠道形态等指标，确定了蜡样芽孢杆菌的最佳使用浓度是10^9CFU/kg；并构建细菌生态网络模型，揭示蜡样芽孢杆菌通过抑制条件致病菌和细菌互作来调节肠道菌群平衡的作用机制；发现活与灭活蜡样芽孢杆菌可通过非Keap1依赖的Nrf2信号通路调节抗氧化反应与抑制肠道炎症，发挥改善肠道健康的作用；证实活与灭活蜡样芽孢杆菌均能通过影响肠道菌群组成调控菌群的营养代谢来调节宿主的代谢过程。通过上述研究，一定程度上揭示了蜡样芽孢杆菌调节肠道菌群平衡及改善肠道细菌营养代谢的作用机制，为其在鱼类养殖上的应用提供了理论依据。