白蚁肠道共生微生物的作用:酵母,一个“隐身”的特别菌群

The role of gut symbionts from termites: a unique hidden player from yeasts

摘要:

长期以来，白蚁对木质纤维素的降解能力令人惊叹，毫无疑问，其在全球碳循环中扮演着一个十分重要的角色。这一强大功能的实现极大地依赖于一种特别的肠道“消化液（digestome）”，它的构成不仅包括了来自白蚁自身产生的木质纤维素降解酶系统，还来源于独特与多样的肠道共生微生物的贡献（包括了古细菌、细菌、酵母以及其他真核生物），它们的协同作用能有效地将木质纤维素生物质高效转化为乙酸、甲烷、二氧化碳、氢气等物质。然而，到目前为止，我们对这类昆虫的独特肠道生物转化系统的认识还很不深入，特别是针对肠道内的那些各类共生微生物菌群的功能、白蚁与共生微生物间的相互关系、以及潜在的科学与应用价值还无法给予明确的科学解释，更不用说针对其肠道中的共生酵母菌群，一类通常被忽略的独特微生物。近20多年来，越来越多的研究证据表明，白蚁肠道共生酵母在与寄主的关系中表现了不可或缺的重要性与独特功能，已被证明广泛分布于不同白蚁及许多其他昆虫的肠道中。随着近20年来越来越多昆虫肠道共生微生物酵母群被发现和鉴定，他们潜在的功能以及与寄主的共生机制被逐步解析，这些研究结果进一步揭示了“隐身”的昆虫肠道酵母类微生物菌群与寄主的营养、关键生物质转化过程中的重要酶系统、转化过程中的关键中间产物的转化与利用、抵御外源性的重要病原物，甚至对白蚁种群繁衍的远缘交配等方面均可能发挥了重要和不可缺少的作用。本文将试图归纳相关研究的最新进展，系统总结与解析白蚁肠道来源共生酵母的重要科学价值及其在不同领域的潜在应用前景。

Abstract:

The capability to degrade lignocellulose in a variety of termite species is important for global carbon recycling on lignocellulosic biomass. This unique capability from termites relies on their special "gut digestome" such as bacterial, archaeal, yeast, or other eukaryotic symbionts. However, to date, their highly specialized gut systems of such insects are not yet fully understood regarding their unique symbiont functions and their potential values applied in biotechnology or other relevant fields, particularly for the group of various yeast symbionts. In recent years, there is a growing evidence to demonstrate the symbiotic yeast importance and their widespread distributions in various termite digestive systems, as well as their unique functions played in termite-symbiont interactions. Along with more yeast species to be identified from insect gut systems in the past two decades, their potential functions and relevant mechanisms interacted with host insects and other gut symbionts have been reported, which may be related to host nutrition, essential enzymes for biomass processing, intermediate chemical compounds, suppressing external pathogens, even colony outbreeding, etc. This review paper would mainly focus on the recent research work on yeast symbionts identified from termite gut and their potential values and functions applied in different fields.