【作者】 张婷； 李德亮； 肖调义；

【Author】 ZHANG Ting, LI DeLiang, XIAO TiaoYi (College of Animal Science and Technology, Hunan Agriculture University, Changsha 410128, China)

【机构】 湖南农业大学动物科学技术学院；

【摘要】 异味是一个在饮用水、水产业中频繁发生的问题,美国、加拿大、日本、澳大利亚、欧洲、南非等地区已均有报道。其中,由蓝藻、放线菌引起的水体土霉异味问题备受关注。土霉异味通常是由化合物二甲萘烷醇(geosmin)和2-甲基异茨醇(2-methylisoborneol,2-MIB)所引起。在水生态系统中,部分蓝藻和放线菌是其主要生物源,绝大多数源水异味与之相关,不仅危及饮用水安全、降低水产品质量,而且增加供水和水产养殖生产成本,对社会、经济的负面影响极大。本研究以产geosmin蓝藻——库氏鞘丝藻(Lyngbya Kuetzingii)为研究对象,通过PCR技术从库氏鞘丝藻(L.Kuetzingii)总DNA中扩增决定geosmin生物合成的倍半萜烯合成酶基因geoL。碱基序列分析表明,该基因包含一个长为2298bp编码765个氨基酸的开放阅读框。氨基酸序列比对分析表明,geoL基因编码蛋白与颤藻(Oscillatoriasp.PCC6506)、乌克兰鱼腥藻(Anabaena ucrainica CHAB2155、A.ucrainica CHAB1432)、点状念珠藻(Nostoc punctiforme PCC73102)、席藻(Phormidium sp.P2r)倍半萜烯合成酶同源性都在84%以上,与粘细菌的同源性介于61%~73%之间,与放线菌的同源性相对最低。geoL基因编码蛋白具两个结构域,其中N-末端结构域是一个具有完整功能的环化酶。综上所述,蓝藻中geosmin的生物合成过程可能与粘细菌更为相似。更多还原

【Abstract】 Off-flavors, especially earthy and musty odors are among the widespread problems in freshwater bodies of different purposes, especially for water supplies and aquaculture, which have been reported in USA, Canada, Japan, Australia, Europe, South Africa, etc. Most of the problems are caused by two major saturated bicyclic terpenoids, namely, geosmin (trans-1,10-dimethyl-trans-9-decalol) and 2-methylisoborneol (1,2,7,7-tetramethyl-exo-bicyclo [2.2.1]-heptan-2-ol or 2-MIB), which are usually produced as secondary metabolites by some actinomycetes, planktonic and periphytic cyanobacteria. Geosmin and 2-MIB may cause significant economic and public health concerns, which not only endanger the safety of drinking water and reduce the aquatic product quality, but also increase water supply and aquaculture production cost. In this study, the PCR has been used to amplify a 2,298-bp ORF from Lyngbya Kuetzingii (UTEX 1547), encoding a protein of 765 amino acids. Sequence alignment of amino acids indicated that the protein coded by gene geoL shared more than 84% homology with the sesquiterpene synthase of Oscillatoria sp. (PCC 6506), Anabaena ucrainica (CHAB 2155), A. ucrainica (CHAB 1432), Nostoc punctiforme (PCC 73102) and Phormidium sp. (P2r); 61%-73% homology with that of myxobacteria, and relative lowest homology with that of actinomycetes. The gene, geoL, codes for a protein with two sesquiterpene synthase domains, and the N-terminal domain is a complete functional terpene cyclase. In conclusion, the geosmin biosynthesis process in Cyanobacteria may more similar to that in myxobacteria than actinomycetes.更多还原