Wang Zhongjie, Xiao Peng, Song Gaofei, Li Yeguang, Li Renhui
Key Laboratory of Plant Germplasm Enhancement and Speciality Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
Environ Sci Pollut Res Int. 2015 Aug;22(16):12133-40. doi: 10.1007/s11356-015-4470-2. Epub 2015 Apr 18.
The earthy-musty compounds geosmin and 2-methylisoborneol (MIB) produced by cyanobacteria are considered as the main biological causes of off-flavor events, especially in aquatic ecosystems. More than 50 filamentous cyanobacteria species have been documented as geosmin or MIB producers; however, little is known about the species coproducing these two metabolites. In this study, an epiphytic sample was collected from a river in Hubei, China. Three isolated strains (A2, B2, and B4) producing earthy odors were successfully isolated and identified as the cyanobacterium Leptolyngbya bijugata Anagnostidis et Komárek 1988 based on morphology and 16S rDNA sequences. Gas chromatography analysis confirmed that the isolated L. bijugata strains were geosmin and MIB coproducers, with accumulation ranging from 13.6 to 22.4 and 12.3 to 57.5 μg L(-1), respectively. The partial fragments of geosmin and MIB synthesis genes in the L. bijugata strains were cloned and sequenced. Further sequences and phylogenetic analysis indicated the high conservation and a common origin of these genes in cyanobacteria. This study is the first to report and characterize the coproduction of geosmin and MIB by L. bijugata, representing a new source for potential risk of off-flavor events.
蓝藻产生的土腥味化合物土臭素和2-甲基异莰醇（MIB）被认为是异味事件的主要生物学原因，尤其是在水生生态系统中。已有超过50种丝状蓝藻被记录为土臭素或MIB的生产者；然而，对于同时产生这两种代谢物的物种却知之甚少。在本研究中，从中国湖北的一条河流中采集了附生样本。成功分离出三株产生土腥味的菌株（A2、B2和B4），并根据形态学和16S rDNA序列鉴定为1988年的双对叶鞘丝藻（Leptolyngbya bijugata Anagnostidis et Komárek）。气相色谱分析证实，分离出的双对叶鞘丝藻菌株同时产生土臭素和MIB，积累量分别为13.6至22.4 μg L(-1)和12.3至57.5 μg L(-1)。克隆并测序了双对叶鞘丝藻菌株中土臭素和MIB合成基因的部分片段。进一步的序列和系统发育分析表明，这些基因在蓝藻中具有高度保守性和共同起源。本研究首次报道并表征了双对叶鞘丝藻同时产生土臭素和MIB，这代表了异味事件潜在风险的一个新来源。
