土壤食细菌线虫取食细菌的偏好性及其分子机制

Bacterial-feeding nematodes play important roles in soil ecosystem by preying bacteria, which not only affects microbial populations, activity and community structures, but also stimulates decomposition of organic matter and mineralization of nitrogen and phosphorus. Therefore, the molecular mechanism of bacterial-feeding nematodes food preference is the key to understand the ecological function mechanism of bacterial-feeding nematodes. In this study, we will first explore the bacterial preference traits of soil indigenous bacterial-feeding nematodes by preying different species of bacteria (employing wildtype C.elegans -the model organism-as control). Next, using transcriptional profiling by microarray, we will choose candidate functional genes regulated in response to different bacterial environments associated with bacterial preference of wildtype C.elegans. Moreover, using C.elegans mutations that lose candidate functional genes, we want to find out the bacterial preference traits of C.elegans mutations by exposing them to the given bacterial environments and validate the relationship between the candidate functional genes with the C.elegans bacterial preference. Based on these experiments, we will make use of RNAi (RNA interference) technology to produce soil indigenous bacterial-feeding nematodes mutations that lose candidate functional genes. Then, exposing the soil indigenous bacterial-feeding nematodes mutations to the given bacterial environments, we would like to detect the bacterial preference traits of these mutations and confirm the relationship between the candidate functional genes with the soil indigenous bacterial-feeding nematodes bacterial preference. So, we can discover the molecular mechanism of bacterial-feeding nematodes food preference and understand the ecological function mechanism of bacterial-feeding nematodes. Furthermore, our results can contribute to futher study of the interaction between bacterial-feeding nematodes with bacteria and the genetic function of bacterial-feeding nematodes in soil ecosystem.

土壤食细菌线虫通过取食细菌，从而调控微生物的数量、活性和群落结构参与土壤C、N、P转化等生态过程。因此研究土壤食细菌线虫取食细菌偏好性的分子机制是揭示土壤食细菌线虫生态功能作用机理的关键。本项目首先研究土著优势食细菌线虫对不同细菌的取食偏好性特征（以模式线虫C.elegans野生种为参照）；然后从模式线虫从发，通过对取食不同细菌的线虫后代的基因芯片（Microarray）对比分析，筛选控制其取食偏好的相关功能基因，并采用其取食偏好相关功能基因缺失的线虫突变体回接到不同细菌培养试验中，验证该功能基因确实与取食偏好相关；在此基础上利用RNAi基因干扰技术使土著优势食细菌线虫的取食偏好相关功能基因沉默，进一步验证该功能基因沉默的线虫对上述不同细菌取食的偏好性，从而确认土壤生态系统中土著食细菌线虫取食偏好的功能基因，为揭示食细菌线虫与细菌相互作用的分子机制和食细菌线虫功能调控的分子手段奠定基础。

土壤食细菌线虫选择性取食土壤细菌，可以改变土壤微生物种间竞争以及微生物在土壤中的分布，对于解释土壤食物网中能量流动、养分转化等具有重要的作用。根据土壤食细菌线虫对细菌的取食存在偏好性，研究其取食偏好性的分子机制是揭示土壤食细菌线虫调控土壤微生物数量、活性和群落结构组成的关键。本项目研究模式线虫C. elegans和土著食细菌线虫(中杆属线虫Mesorhabditis sp. NJ、拟丽突属线虫Acrobeloides sp. NJ)的取食偏好性及其表型特征；使用供试细菌喂食驯化C. elegans，研究驯化后的C. elegans的取食偏好及取食相关功能基因表达的变化；利用RT-PCR和RACE的方法，从土著食细菌线虫中克隆出取食相关功能基因，使用供试细菌喂食驯化土著食细菌线虫，研究驯化后的土著食细菌线虫的取食偏好性及取食相关功能基因表达的变化，同时利用RNAi技术使土著食细菌线虫取食相关功能基因沉默，观察基因沉默后线虫取食偏好性及其余取食相关基因表达量的变化。研究发现，土壤食细菌线虫自由取食不同细菌时具有明显的取食偏好性，且模式线虫C. elegans和土著食细菌线虫均偏爱繁殖快、呼吸释放CO2浓度高的活跃细菌；以不同的细菌喂食驯化食细菌线虫后，线虫取食相关功能基因的表达量和取食的偏好性均会发生改变；运用RNAi技术可以有效抑制线虫Acrobeloides sp. NJ中取食相关功能基因的表达，且功能基因沉默后的Acrobeloides sp. NJ的取食偏好发生改变。本研究从模式线虫C. elegans和土著食细菌线虫对细菌取食的选择性和偏好性出发，探究食细菌线虫取食相关基因的表达量的变化，明确食细菌线虫取食偏好性的相关功能基因，揭示食细菌线虫与细菌相互作用的内在分子机制并为土壤食细菌线虫功能调控的分子手段提供理论依据。

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