Acta Entomologica Sinica ›› 2019, Vol. 62 ›› Issue (11): 1325-1334.doi: 10.16380/j.kcxb.2019.11.010

• REVIEW ARTICLES • Previous Articles     Next Articles

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

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