Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O.Box 12, 76100, Rehovot, Israel.
Division of Research, Florida Atlantic University, 777 Glades Road, Boca Raton, FL, 33431, USA.
Curr Microbiol. 2020 Mar;77(3):353-360. doi: 10.1007/s00284-019-01844-z. Epub 2019 Dec 12.
The secondary metabolites geosmin and 2-methylisoborneol (MIB) are known to taint fish with an undesirable, earthy-muddy taste and odor. In an earlier study on a zero-discharge recirculating aquaculture system (RAS), it was found that geosmin and MIB were removed by microbial communities residing in sludge from the digestion basin of the system. In the present study, 16S amplicon sequencing was used to identify changes in relative abundances of bacterial taxa in geosmin and MIB-enriched crude sludge. The removal of geosmin and MIB by the sludge was accompanied by increased abundances of 12 operational taxonomic units (OTUs). The most prominent increase in abundances was recorded for OTUs affiliated with bacterial genera known to harbor denitrifiers. Among these were the Betaproteobacteria genera Thauera, which utilizes terpenes to fuel denitrification, and Comamonas, which was previously isolated from the digestion basin of the same system and is capable of growth on geosmin and MIB as sole carbon and energy sources. Thus far, denitrification has been associated with bacteria capable of utilizing terpenes other than geosmin and MIB. The significant increase in the abundance of denitrifying bacterial genera in sludge in which geosmin and MIB comprised only 0.06% of the total carbon content might indicate that such bacteria play a major role in the removal of these compounds in anoxic environments.
土臭素和 2-甲基异莰醇（MIB）是两种已知的次生代谢物，会使鱼类产生不良的泥土味和土腥味。在一项关于零排放循环水产养殖系统（RAS）的早期研究中，发现系统消化池中的污泥微生物群落可以去除土臭素和 MIB。在本研究中，使用 16S 扩增子测序来鉴定富集土臭素和 MIB 的粗污泥中细菌分类群相对丰度的变化。污泥对土臭素和 MIB 的去除伴随着 12 个操作分类单元（OTU）丰度的增加。丰度增加最显著的是与已知含有反硝化菌的细菌属相关的 OTU。其中包括利用萜类化合物进行反硝化作用的β变形菌属的陶厄氏菌，以及先前从同一系统的消化池分离出来的贪噬菌属，它能够以土臭素和 MIB 作为唯一的碳源和能源进行生长。到目前为止，反硝化作用一直与能够利用萜类化合物而不是土臭素和 MIB 的细菌有关。在土臭素和 MIB 仅占总碳含量 0.06%的污泥中，反硝化细菌属的丰度显著增加，这可能表明这些细菌在缺氧环境中去除这些化合物中发挥了主要作用。
