昆虫学报 ›› 2019, Vol. 62 ›› Issue (11): 1325-1334.doi: 10.16380/j.kcxb.2019.11.010

• 综 述 • 上一篇    下一篇

培菌白蚁菌圃微生物降解木质纤维素的研究进展

梁世优1, 王成盼1, 殷学杰1, 李鸿杰1,2, 莫建初1,*   

  1. (1. 浙江大学昆虫科学研究所, 农业部农业昆虫学重点实验室, 杭州 310058; 2. Department of Bacteriology, University of WisconsinMadison, Madison WI 53706, USA)
  • 出版日期:2019-11-20 发布日期:2019-11-05

Advances in the degradation of lignocellulose by microbes in fungus combs of fungus-cultivating termites

LIANG Shi-You1, WANG Cheng-Pan1, YIN Xue-Jie1, LI Hong-Jie1,2, MO Jian-Chu1,*   

  1. (1. Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China; 2. Department of Bacteriology, University of WisconsinMadison, Madison WI 53706, USA)
  • Online:2019-11-20 Published:2019-11-05

摘要:  白蚁及其共生微生物协同降解植物细胞壁的机理一直被世界各国科学家所关注。培菌白蚁作为高等白蚁,相比低等食木白蚁具有更多样化的食性,其利用外共生系统“菌圃”,对多种植物材料进行处理。本文综述了菌圃微生物降解木质纤维素的研究进展,以期为深入研究菌圃中木质纤维素降解过程及其机制,并挖掘利用菌圃降解木质纤维素的能力及仿生模拟菌圃开发新的生物质利用系统提供参考。培
菌白蚁在其巢内利用由植物材料修建的多孔海绵状结构——“菌圃”来培养共生真菌鸡枞菌Termitomyces spp.,形成了独特的木质纤维素食物降解和消化策略,使木质纤维素在培菌白蚁及其共生微生物协同作用下被逐步降解。幼年工蚁取食菌圃上的共生真菌菌丝组成的小白球和老年工蚁觅得食物并排出粪便堆积到菌圃上成为上层菌圃。这一过程中,被幼年工蚁取食的共生真菌释放木质素降解酶对包裹在植物多糖外部的木质素屏障进行解聚。菌圃微生物(包括共生真菌)对解聚的木质素基团进一步降解,将多糖长链或主链剪切成短链,使菌圃基质自下而上被逐步降解。最后下层的老熟菌圃被老年工蚁取食,其中肠的内源酶系及后肠微生物将这些短链进一步剪切和利用。因此,蚁巢菌圃及其微生物是培菌白蚁高效转化利用木质纤维素的基础。化学层面的研究表明,菌圃能够实现对植物次生物质解毒和植
物纤维化学结构解构。对共生真菌相关酶系的研究显示可能其在菌圃的植物纤维化学结构和植物次生物质的降解中发挥了作用,但不同属共生真菌间其效率和具体功能不尽相同。而菌圃中的细菌是否发挥了作用和哪些细菌类群发挥了作用等仍有待进一步的研究。相比于低等食木白蚁利用其后肠共生微生物降解木质纤维素,培菌白蚁利用菌圃降解木质纤维素具有非厌氧和能处理多种类型食物两大优势,仿生模拟菌圃降解木质纤维素的机制对林地表面枯枝落叶的资源化利用具有重要意义。


关键词: 培菌白蚁, 菌圃, 微生物, 木质纤维素, 共生真菌

Abstract: The mechanism that termites and their symbiotic microorganisms synergistically degrade the lignocellulose-rich cell wall of plant has been well noticed and investigated by scientists around the world. Higher termites with fungus-cultivating ability have more diverse diets than lower termites. In this article, we reviewed the advances in the degradation of lignocellulose by microbes in fungus combs, so as to provide some references for a better understanding of the process and mechanism of the lignocellulose degradation in fungus combs, exploring the lignocellulosedegrading capacity of fungus combs, and developing biomimetic system of fungus combs to utilize biomass. Fungus-cultivating termites rely on the external symbiotic system, fungus combs, to degrade diverse plant materials. Funguscultivating termites cultivate their symbiotic fungi, Termitomyces spp., on the spongy structure, fungus combs built by plant materials. They develop specific food processing to degrade lignocelluloses gradually with the cooperation of symbiotic microbes. Younger workers ingest food foraged by older workers together with nodules of symbiotic fungi from combs, and excrete primarily feces to establish fresh combs on the surface of combs. In the gut passage of younger workers, Termitomyces release lignin-degrading enzymes to break the lignin barrier. Then, microbes including Termitomyces decompose lignin further, and turn polysaccharides to short chains, making the substrates of combs degraded from bottom to top. Finally, mature combs in the bottom are consumed by older workers. Endogenous enzymes of the midgut and microbes in the hindgut utilize the short chains. In conclusion, fungus combs and their microbes are fundamental for fungus-cultivating termites to utilize lignocelluloses efficiently. Studies of chemical changes in fungus comb indicated that fungus comb can decompose lignocelluloses and detoxify plant secondary compounds. Termitomyces might play a role in these processes, but the efficiency and specific functions vary in different genera of symbiotic fungi. Meanwhile, the specific functions of comb microbes require further investigation. Unlike lower wood-feeding termites which utilize lignocelluloses with the assistance of symbiotic microbes in the hindgut, fungus-cultivating termites degrade lignocelluloses based on fungus comb with two advantages, no requirement for anaerobic environment and fewer limits of food types. Imitation of fungus comb to process lignocelluloses is of great significance for the recycling use of dead wood and fallen leaves in forests.

Key words: Fungus-cultivating termite, fungus comb, microbe, lignocellulose, symbiotic