Syntrophic entanglements for propionate and acetate oxidation under thermophilic and high-ammonia conditions

作者：Abhijeet Singh, Anna Schnürer, Jan Dolfing, Maria Westerholm · 发表于：The ISME Journal · 年份：2023 · DOI：10.1038/s41396-023-01504-y · 被引用次数：73 · 研究领域：Subcritical and Supercritical Water Processes、Chemical Reactions and Isotopes、Innovative Microfluidic and Catalytic Techniques Innovation

Abstract Propionate is a key intermediate in anaerobic digestion processes and often accumulates in association with perturbations, such as elevated levels of ammonia. Under such conditions, syntrophic ammonia-tolerant microorganisms play a key role in propionate degradation. Despite their importance, little is known about these syntrophic microorganisms and their cross-species interactions. Here, we present metagenomes and metatranscriptomic data for novel thermophilic and ammonia-tolerant syntrophic bacteria and the partner methanogens enriched in propionate-fed reactors. A metagenome for a novel bacterium for which we propose the provisional name ‘Candidatus Thermosyntrophopropionicum ammoniitolerans’ was recovered, together with mapping of its highly expressed methylmalonyl-CoA pathway for syntrophic propionate degradation. Acetate was degraded by a novel thermophilic syntrophic acetate-oxidising candidate bacterium. Electron removal associated with syntrophic propionate and acetate oxidation was mediated by the hydrogen/formate-utilising methanogens Methanoculleus sp. and Methanothermobacter sp., with the latter observed to be critical for efficient propionate degradation. Similar dependence on Methanothermobacter was not seen for acetate degradation. Expression-based analyses indicated use of both H2 and formate for electron transfer, including cross-species reciprocation with sulphuric compounds and microbial nanotube-mediated interspecies interactions. Batch cultivati...