Role of the Termite Gut Microbiota in Symbiotic Digestion
Role of the Termite Gut Microbiota in Symbiotic Digestion
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DOI：
10.1007/978-90-481-3977-4_16
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发表时间：
2011-01-01
期刊：
影响因子：
--
通讯作者：
Ohkuma, Moriya
中科院分区：
文献类型：
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作者：
Brune, Andreas;Ohkuma, Moriya
白蚁肠道共生菌群在木质纤维素消化和氮代谢中起着重要作用。白蚁具有双重纤维素分解系统：在较低的白蚁的纤维素酶是由昆虫和它的肠道鞭毛虫，而在较高的白蚁，宿主纤维素酶和后肠细菌参与纤维消化。通常，微生物的摄食链由碳水化合物的初级发酵驱动。然而，在土壤喂养类群中，它们利用土壤有机物质的肽组分作为膳食资源，并且沿着它们高度分隔的肠道沿着显示出明显的理化条件差异，氨基酸是微生物群的重要底物。氢似乎是所有白蚁后肠发酵的中心中间体。在木材饲养类群，它是有效地回收homoacetogenic螺旋体，其中占上风的产甲烷古菌可能是因为他们的能力，定殖的体积的后肠，而产甲烷菌仅限于特定的微生物在后肠壁或肠道鞭毛虫。作为一般规则，微生物种群和代谢活动的空间分离引起代谢物的陡峭梯度。氧气持续流入后肠会影响微氧外围的微生物代谢，肠道中心的缺氧状态仅通过需氧和厌氧微生物快速减少氧气来维持。木质素在肠道通过过程中没有显着矿化，但多酚的修饰过程尚未表征可能会增加木质纤维素和腐殖物质的消化率。在以木材为食的白蚁中，肠道微生物群固定和提升氮并回收含氮废物。负责这些反应的微生物大多是未知的，但最近的研究表明，肠道鞭毛虫的细菌外共生体和内共生体在低等白蚁的氮代谢中起着重要作用。
The symbiotic gut microbiota of termites plays important roles in lignocellulose digestion and nitrogen metabolism. Termites possess a dual cellulolytic system: in lower termites the cellulases are contributed by both the insect and its gut flagellates, whereas in higher termites, host cellulases and hindgut bacteria participate in fiber digestion. Commonly, the microbial feeding chain is driven by the primary fermentations of carbohydrates. However in soil-feeding taxa, which exploit the peptidic component of soil organic matter as a dietary resource and show pronounced differences in physiochemical conditions along their highly compartmented intestinal tract, amino acids are an important substrate for the microbiota. Hydrogen appears to be the central intermediate in the hindgut fermentations in all termites. In wood-feeding taxa, it is efficiently recycled by homoacetogenic spirochetes, which prevail over methanogenic archaea probably because of their ability to colonize the bulk volume of the hindgut, whereas methanogens are restricted to particular microniches at the hindgut wall or within the gut flagellates. As a general rule, the spatial separation of microbial populations and metabolic activities gives rise to steep gradients of metabolites. The continuous influx of oxygen into the hindgut affects microbial metabolism in the microoxic periphery, and the anoxic status of the gut center is maintained only by the rapid reduction of oxygen by both aerobic and anaerobic microorganisms. Lignin is not significantly mineralized during gut passage, but modification of polyphenols by processes yet uncharacterized may increase the digestibility of both lignocellulose and humic substances. In wood-feeding termites, gut microbiota fix and upgrade nitrogen and recycle nitrogenous waste products. The microorganisms responsible for these reactions are mostly unknown, but recent studies have indicated that bacterial ectosymbionts and endosymbionts of the gut flagellates play a major role in the nitrogen metabolism of lower termites.