Geosmin and 2‐methylisoborneol (MIB) are known to cause taste‐and‐odour problems in recirculating aquaculture systems (RAS). Both geosmin and MIB are microbial metabolites belonging to terpenoids. Precursors for terpenoids are biosynthesized via the methylerythritol phosphate (MEP) and the mevalonate (MVA) pathways. We carried out a metagenomic analysis of 50 samples from five RAS to investigate terpenoid biosynthesis and metabolic potential for geosmin and MIB production in RAS microbiomes. A total of 1008 metagenome‐assembled genomes (MAGs) representing 26 bacterial and three archaeal phyla were recovered. Although most archaea are thought to use the MVA pathway for terpenoid precursor biosynthesis, an Iainarchaeota archaeal MAG is shown to harbour a complete set of genes encoding the MEP pathway but lacking genes associated with the MVA pathway. In this study, a total of 16 MAGs affiliated with five bacterial phyla (Acidobacteriota, Actinobacteriota, Bacteroidota, Chloroflexota, and Myxococcota) were identified as possessing potential geosmin or MIB synthases. These putative taste and odour producers were diverse, many were taxonomically unidentified at the genus or species level, and their relative abundance differed between the investigated RAS farms. The metagenomic study of the RAS microbiomes revealed a previously unknown phylogenetic diversity of the potential to produce geosmin and MIB.

中文翻译：

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宏基因组学揭示了在循环水产养殖系统中跨多个细菌门生产土臭素和 2-甲基异冰片的潜力


已知土臭素和 2-甲基异冰片 （MIB） 会导致循环水产养殖系统 （RAS） 中出现味觉和气味问题。土臭素和 MIB 都是属于萜类化合物的微生物代谢产物。萜类化合物的前体通过磷酸甲基赤藓糖醇 （MEP） 和甲羟戊酸酯 （MVA） 途径进行生物合成。我们对来自 5 个 RAS 的 50 个样本进行了宏基因组分析，以研究 RAS 微生物组中土臭素和 MIB 产生的萜类生物合成和代谢潜力。共回收了 1008 个宏基因组组装基因组 （MAG），代表 26 个细菌门和 3 个古细菌门。尽管大多数古细菌被认为使用 MVA 途径进行萜类前体生物合成，但 Iainarchaeota 古细菌 MAG 显示含有一组编码 MEP 通路的完整基因，但缺乏与 MVA 通路相关的基因。在这项研究中，共有 16 个 MAGs 隶属于 5 个细菌门 （酸杆菌门、放线杆菌门、拟杆菌门、绿菟苣和粘球菌门） 具有潜在的土臭素或 MIB 合酶。这些推定的味道和气味生产者是多种多样的，许多在属或种水平上分类学上未被鉴定，并且它们的相对丰度在所调查的 RAS 农场之间有所不同。RAS 微生物组的宏基因组研究揭示了以前未知的系统发育多样性，即产生土臭素和 MIB 的潜力。