亚热带森林土壤分子生态网络中粘细菌-细菌捕食关系的解析

Myxobacteria is one of the most abundant taxa in soil, and the predatory interaction between myxobacteria and prey bacteria is also one of the most important interactions existing in soil. The combined use of high-throughput sequencing and ecological molecular network has been developed recently. However, the interaction network analysis has more often served as a visual means to compare microbial communities from different environments than as a mean to appreciate microbial interactions associated with certain ecological processes. Previous studies often described a subnetwork as a functional related unite, but the authenticity of the interactions and the real functionality in ecological context have seldomly been evidenced. Therefore, it is necessary to explore the potential interactions in the network and figure out those interactions that are real ecological processes. Based on the predatory interaction, we isolated more than 300 myxobacterial strains from subtropical forest soil and litter using prey as induction, indicating this interaction is common in this area. This project will collect soil samples from different climate zones and different layers in the virgin forests in Guangdong province, focusing on the interactions between myxobacteria and other soil bacteria based on ecological molecular network. The predation interactions are distinguished from the predicted network using isolation of potential prey bacteria from soil samples. And efficient prey bacteria will be confirmed. The certain predatory processes will be confirmed by the induction of myxobacteria using the obtained efficient prey bacteria. The results from this project will help to identify ecologically meaningful predatory associations between myxobacteria and prey bacteria, which will promote the isolation of the uncultured myxobacterial resources.

粘细菌是土壤中最主要的类群之一，其捕食关系是土壤主要的互作关系之一。近年来，采用基于高通量测序的分子生态网络研究群落水平上微生物间的互作关系开始发展起来，然而，目前相关研究仅停留在描述阶段，网络预测关系的可靠性有待证实。因此有必要对分子生态网络提供的潜在互作关系进行深度解析，确定环境中真实发生的互作。本项目组利用捕食关系已从热带亚热带森林分离了300多株粘细菌，表明该生境中粘细菌-细菌捕食关系的普遍存在。因此本项目拟采集中、南亚热带森林土壤及土壤剖面样品，以粘细菌-细菌互作关系为研究对象，基于免培养方法构建细菌分子生态互作网络；通过分离样品中的潜在被捕食菌，辨识分子生态网络中的粘细菌-细菌捕食关系，获得高效的被捕食菌；用高效被捕食菌诱导粘细菌子实体的形成，解析森林土壤不同环境中的真实捕食关系。研究结果能够将预测的互作关系与实际的生物学关系联系起来，进而推动粘细菌这一难培养菌的新资源挖掘。

粘细菌是一类广泛分布于土壤中丰度较高的捕食性细菌类群之一，也是一类重要的药源微生物。利用粘细菌的捕食性诱导子实体是其主要分离方法，但是目前基于辅助菌的粘细菌分离方法存在很大的盲目性和不确定性。本项目以粘细菌-细菌互作关系为研究对象，发现热带亚热带森林土壤是粘细菌的重要生境，揭示了局域粘细菌群落的生态分布特征，土壤其他细菌群落组成和结构等生物因素的加入提高了不同样地粘细菌群落结构差异的可解释程度，为通过粘细菌捕食细菌这一生态角色创新粘细菌分离方法提供了理论依据。基于免培养方法构建细菌分子生态互作网络，筛选出革兰氏阳性菌球形节杆菌Arthrobacter globiformis GDMCC 1.1730作为新型辅助菌，并在捕食培养基上验证其捕食活性，建立了基于细菌分子生态网络和平板捕食的粘细菌分离方法。以新型辅助菌作为辅助菌进行粘细菌的分离，诱导出11种粘细菌子实体，且包括一些仅由GDMCC 1.1730诱导而大肠杆菌未能诱导出的子实体。最终纯化出了7个属、12个种共78株粘细菌，为获取自主知识产权新药源微生物的开发与研究提供了资源基础。进一步，本研究分离到粘细菌资源的抑菌功能筛选实验鉴定到一株粘细菌新属新物种，并揭示了利用其捕食特性抑菌植物病原菌的生物学基础包括利用小分子天然产物抑制丝状病原真菌的抑制策略、利用胞外蛋白裂解病原细菌的捕食策略。