Department of Ecological Microbiology, University of Bayreuth, 95440 Bayreuth, Germany.
FEMS Microbiol Ecol. 2019 Feb 1;95(2). doi: 10.1093/femsec/fiy221.
Earthworms have profound impact on soil-based ecosystems. Although theoretical considerations suggest that most microbes in the earthworm gut are likely ingested and transient, the non-responsiveness of soil microbes to a specific high value gut nutrient and anoxia has made it difficult to demonstrate that responsive gut fermenters are derived from soil. Therefore, soil and gut content of the model earthworm Lumbricus terrestris were examined for their fermentative capabilities. In unsupplemented anoxic microcosms, fermentation was negligible with soil but rapid with gut content. However, both soil and gut content facilitated robust fermentations when challenged with complex nutrients indicative of those released from gizzard-disrupted cells. Based on the relative abundances of 16S rRNA and 16S rRNA gene sequences, the responsive fermentative taxa in unsupplemented gut content treatments were negligible in unsupplemented soil treatments. In contrast, the responsive fermentative taxa in soil and gut content treatments supplemented with complex nutrients displayed marked similarities, with numerous Proteobacteria- and Firmicutes-affiliated phylotypes being dominant. These findings indicated that detectable differences between the fermentative taxa in soil and gut contents are due in part to the nutrient-dependent metabolic status of community members and reinforce the likelihood that ingested transient microbes contribute to fermentation in the alimentary canal.
蚯蚓对基于土壤的生态系统有深远的影响。虽然理论上认为蚯蚓肠道中的大多数微生物可能是被摄入并短暂存在的，但土壤微生物对特定高价值肠道养分和缺氧的无反应性使得很难证明有反应性的肠道发酵者是来自土壤的。因此，对模式蚯蚓（Lumbricus terrestris）的土壤和肠道内容物进行了发酵能力的研究。在未补充缺氧微宇宙中，土壤中的发酵作用可以忽略不计，但肠道内容物中的发酵作用迅速。然而，当用复杂的养分（提示那些从肌胃破裂细胞释放出来的养分）进行挑战时，土壤和肠道内容物都促进了强大的发酵作用。基于 16S rRNA 和 16S rRNA 基因序列的相对丰度，在未补充养分的肠道内容物处理中，响应性发酵类群在未补充养分的土壤处理中可以忽略不计。相比之下，在补充了复杂养分的土壤和肠道内容物处理中，响应性发酵类群显示出显著的相似性，许多与变形菌门和厚壁菌门相关的分类群占据优势。这些发现表明，土壤和肠道内容物中发酵类群之间的可检测差异部分归因于社区成员的营养依赖性代谢状态，并加强了摄入的短暂微生物对消化道发酵的贡献的可能性。
