淡水藻种库(FACHB)库藏产2-MIB蓝藻的鉴定及其产嗅特征研究

IDENTIFICATION AND CHARACTERIZATION OF 2-MIB-PRODUCING CYANOBACTERIA IN FACHB

为认识产二甲基异莰醇(2-MIB)蓝藻的形态和产嗅特征,从国家水生生物种质资源库淡水藻种库中筛选出24株可产2-MIB藻株,描述了这些藻株的形态特征和生境分布。结合形态和16S rRNA基因分析对藻株进行物种鉴定复核,修订了部分库藏藻株物种名称,例如发现库藏产2-MIB的浮丝藻属种类应当被重新鉴定为拉氏拟浮丝藻或索状气丝藻。基于mic基因系统发育树分析,显示蓝藻mic基因形成5个分支。通过2-MIB含量检测发现,不同藻株间单个细胞总2-MIB含量为6—2549 fg/cell,其含量通常为拉氏拟浮丝藻>索状气丝藻>灰假鱼腥藻。研究提供了产2-MIB蓝藻的形态、分子、生态和产嗅特性等的基础数据,首次报道气丝藻、沙丝藻、苏打丝藻种类可产2-MIB,并在国内首次报道了产2-MIB的微鞘藻,为进一步研究产2-MIB蓝藻生理生态特性提供重要的实验材料和科学依据。

Odor problems in freshwater caused by 2-methylisoborneol(2-MIB)have received much attention in China recently.The odorous 2-MIB in freshwater is known to be mainly produced by a group of filamentous cyanobacteria which cause offensive taste and odor in drinking water and fish catch.From the detection of MIB synthase gene and GC/MS analyses,24 strains of 2-MIB-producing cyanobacteria were detected in Freshwater Algae Culture Collection at the Institute of Hydrobiology(FACHB-collection),National Aquatic Biological Resource Center,the largest microalgal culture collection in China.These strains were re-identified as Planktothricoides raciborskii(Wołoszyńska)Suda&Watanabe,Aerosakkonema funiforme Thu&Watanabe,Pseudanabaena cinerea Tuji&Niiyama,Oscillatoria lutea var.contorta Baker et Bold,Microcoleus sp.,Desertifilum tharense Dadheech&Krienitz and Sodalinema sp.by morphological descriptions and molecular characteristics based on the 16S rRNA gene,respectively.Most 2-MIB-producing strains of Planktothrix in FACHB-collection should be re-identified as P.raciborskii or A.funiforme.This was the first report of 2-MIB-producing filamentous cyanobacteria of Aerosakkonema,Desertifilum and Sodalinema in the world,and was also the first report of 2-MIB-producing Microcoleus in China.The phylogenetic analyses base on 16S rRNA gene indicated that 2-MIB-producing strains in FACHB-collection were placed on seven separated clades,which reflected true taxonomic relationships.The genera Planktothricoides,Aerosakkonema,Pseudanabaena,Microcoleus,Desertifilum and Sodalinema formed six monophyletic clades in 16S rDNA tree;however,O.lutea var.contorta was closely related to some strains of Oscillatoria,Phormidium and Kamptonema.The phylogenetic analyses based on mic gene indicated that 2-MIB-producing cyanobacteria strains formed five clades with high support values.2-MIB-producing P.raciborskii and A.funiforme were clustered into Clade I in mic tree.Two 2-MIB-producing Microcoleus strains were placed on CladeⅡandⅢ,respectively.All 2-MIB-producing Pseudanabaena strains were clustered into CladeⅣ.Phylogenetic topology of some 2-MIB-producing strains in mic tree were incongruent with the topology in 16S rDNA tree.Cell quota of 2-MIB produced by these strains may vary in a wide range,varying from 6—2549 fg/cell.Cell quota of 2-MIB varied considerably among species,such as P.raciborskii>A.funiforme>P.cinerea.The results provide important experimental materials and basic data on morphological,molecular,ecological and 2-MIB-producing characteristics of filamentous cyanobacteria,and contribute to understanding ecophysiological characteristics 2-MIB-producing cyanobacteria.