Chain elongation is a growth-dependent anaerobic metabolism that combines acetate and ethanol into butyrate, hexanoate, and octanoate. While the model microorganism for chain elongation, Clostridium kluyveri, was isolated from a saturated soil sample in the 1940s, chain elongation has remained unexplored in soil environments. During soil fermentative events, simple carboxylates and alcohols can transiently accumulate up to low mM concentrations, suggesting in situ possibility of microbial chain elongation. Here, we examined the occurrence and microbial ecology of chain elongation in four soil types in microcosms and enrichments amended with chain elongation substrates. All soils showed evidence of chain elongation activity with several days of incubation at high (100 mM) and environmentally relevant (2.5 mM) concentrations of acetate and ethanol. Three soils showed substantial activity in soil microcosms with high substrate concentrations, converting 58% or more of the added carbon as acetate and ethanol to butyrate, butanol, and hexanoate. Semi-batch enrichment yielded hexanoate and octanoate as the most elongated products and microbial communities predominated by C. kluyveri and other Firmicutes genera not known to undergo chain elongation. Collectively, these results strongly suggest a niche for chain elongation in anaerobic soils that should not be overlooked in soil microbial ecology studies.

链延长是一种依赖于生长的厌氧代谢，它将乙酸盐和乙醇结合成丁酸盐、己酸盐和辛酸盐。而链伸长的模型微生物，克鲁维梭菌，在 1940 年代从饱和土壤样本中分离出来，链伸长在土壤环境中仍未得到探索。在土壤发酵过程中，简单的羧酸盐和醇类可以瞬时积累至低 mM 浓度，这表明微生物链延长的原位可能性。在这里，我们检查了微观世界中四种土壤类型中链伸长的发生和微生物生态学以及用链伸长底物修正的富集物。在高浓度 (100 mM) 和环境相关 (2.5 mM) 的醋酸盐和乙醇浓度下孵育数日后，所有土壤均显示出链伸长活性的证据。三种土壤在底物浓度高的土壤微观世界中表现出显着的活性，将 58% 或更多的添加碳以乙酸盐和乙醇的形式转化为丁酸盐、丁醇和己酸盐。C. kluyveri和其他未知的Firmicutes属会发生链伸长。总的来说，这些结果强烈表明厌氧土壤中链伸长的生态位，这在土壤微生物生态学研究中不应被忽视。