黑翅土白蚁和黄翅大白蚁差异化利用林地生物质的微生物学机理研究

Increasing attention has been paid to exploring lignocellulolytic enzymes and microbes from termites and their symbiotic systems for potential uses in conversion of lignocellulose into biofuels. To date, the wood-feeding termite has been well explored and high quantity of enzymes or microbes have been mined thereof. However, due to the dietary differences of different termite groups, and the various secondary metabolites and lignocellulosic structures in plant materials, comparable study of termites with different feeding-habits is needed. Fungus-growing termites specifically cultivate Termitomyces spp. on their fungus comb, which could pre-degrade lignocellulose for their host. Moreover, fungus-growing termites demonstrate different feeding habits, in which Macrotermes barneyi prefers hardwood litter while Odontotermes formosanus prefers branches or living trees. Here, based on our laboratory artificial rearing system for fungus-growing termite and by using pyrosequencing, NMR technology etc., symbiotic roles of their fungus comb microbes in degradation of plant secondary metabolite and lignocellulosic structure were studied, microbial community corresponding to different plant materials were investigated. These results could not only provide a good quantity of novel strains with potential use in litter utilization, but also provide evidences for probing symbiotic mechanisms underlying termite host ecological niche, and are critical to improving termite control.

开发利用白蚁共生系统的木质纤维素降解酶系、菌系一直是科学研究热点。目前在木食性白蚁已取得突破，获得一些可高效转化生物质的微生物和酶制剂。鉴于白蚁食性的多样性及植物原料中次生物质和化学结构的复杂性，开展不同食性白蚁的比较研究对进一步发展生物质转化意义重大。培菌白蚁是我国南方苗圃地和新造林地中重要害虫，它在巢内菌圃上培养鸡枞菌来帮助自身降解植物食料。生物学观测表明培菌白蚁中黄翅大白蚁喜食阔叶类落叶，黑翅土白蚁则不取食阔叶类落叶而喜食立木或枯枝。为探明上述白蚁食性差异内在机制，本项目拟基于课题组建立的培菌白蚁室内饲养系统，通过核磁共振和高通量测序等方法研究上述两类白蚁的菌圃微生物，阐明菌圃微生物对次生物质和化学结构降解能力的差异，解析微生物类群对植物原料的响应。该研究将可解析菌圃微生物帮助宿主占据独特生态位的机理，也将为枯枝落叶等农林废弃物资源化利用及开发林地白蚁防治新技术提供思路。

开发利用白蚁共生系统的木质纤维素降解酶系、菌系一直是科学研究热点。鉴于白蚁食性的多样性及植物原料中次生物质和化学结构的复杂性，开展不同食性白蚁的比较研究对进一步发展生物质转化意义重大。培菌白蚁是我国南方苗圃地和新造林地中重要害虫，它在巢内菌圃上培养鸡枞菌来帮助自身降解植物食料。本项目综合运用植物全胞壁二维核磁共振、热裂解气相色谱和高通量测序等技术研究培菌白蚁中黄翅大白蚁喜食阔叶类落叶，黑翅土白蚁则不取食阔叶类落叶而喜食立木或枯枝的微生物机制。发现黑翅土白蚁的年轻工蚁可快速打开木质素的碳-碳化学键并利用半纤维素侧链上的糖作为食物，彻底解除多糖组分中纤维素和半纤维素的外部物理屏障，巢内菌圃上的真菌和细菌则将多糖组分剪切至更易降解利用的寡糖，年老工蚁取食富含寡糖的菌圃作为食物。通过细菌16sRNA基因的高通量测序，对黑翅土白蚁巢内和肠道内共生微生物群落结构进行研究，发现了年轻工蚁和年老工蚁肠道细菌群落结构差异，特别是具有木质纤维素侧连降解能力的菌株Lachnospiraceae专属性在年轻工蚁中富集，而具有寡糖降解能力的Rikenellaceae是年老工蚁肠道的优势菌株。此外，板栗边材和板栗叶的比较研究表明叶片中木质素组分较边材简单，不含S型紫丁香基木质素，且富含芸香苷。喂食研究表明黄翅土白蚁菌圃微生物更适应富含次生代谢物纤维原料，槲皮素和芸香苷等次生物质存在对其降解木质素能力没有影响。同时，发现细菌群落对纤维原料次生代谢物响应显著，进而分离培养了约15个有降解功能活性的菌株。然而，黑翅土白蚁菌圃微生物更适应木屑等木质素结构复杂的原料，植物次生物质对其生理功能影响显著。相关研究成果为解析菌圃微生物帮助宿主白蚁占据独特生态位的提供理论，为发展生物能源的提供新型微生物菌剂，为提出农林废弃物的资源化开发利用利用提供科学依据。