Morphological diversity and molecular characteristics of bloom forming <i>Dolichospermum</i> species in Lake Zhelin, Jiangxi Province

Abstract

长孢藻是具有产多种蓝藻毒素及异味物质潜在能力的丝状异形胞蓝藻.为了探究长孢藻的生物学特性，我们从江西柘林湖分离24株长孢藻，经形态鉴定分成4个种类，分别为浮游长孢藻（Dolichospermum planctonicum）、近亲长孢藻（D.affine）、卷曲长孢藻（D.circinale）、螺旋长孢藻（D.spiroides）.16S rRNA基因序列表明柘林湖长孢藻与日本等地区的长孢藻高度相似，但只有近亲长孢藻与日本近亲长孢藻在分子系统进化树上聚为一支.基于16S-23S rRNA之间高变异性的ITS序列分析，4种长孢藻的D1-D1'螺旋结构相同，藻丝为直型的浮游长孢藻、近亲长孢藻与藻丝为弯型的卷曲长孢藻、螺旋长孢藻的Box-B、V3螺旋结构差异较大.通过对毒素和异味的分子生物学检测显示24株长孢藻均不产毒，但是4株浮游长孢藻及1株卷曲长孢藻含有土腥素合成基因.本研究不仅对柘林湖水华蓝藻的多样性以及潜在生态风险提供科学的基础资料，也在流域层面上为鄱阳湖的水生态系统研究和保护提供了一定的科学基础.;Dolichospermum is a filamentous cyanobacterial genus with the potential capacity to produce multi-cyanotoxins and taste and odour (T/O) compounds. Twenty-four strains of Dolichospermum isolated from Lake Zhelin, Jiangxi were morphologically and molecularly characterized for exploring the biological properties of Dolichospermum species. They were classified into four species as D. planctonicum, D. affine, D. circinale and D. spiroides. Phylogenetic analysis based on the 16S rRNA sequences showed that all Dolichospermum strains here were highly similar to the strains isolated from Japan and other regions, but only D. affine was well grouped into one cluster. Based on the secondary structures of 16S-23S ITS, all the Dolichospermum strains showed to have the same structures in D1-D1' region. In Box-B and V3 regions, the structures of D. planctonicum and D. affine were different from those of D. circinale and D. spiroides, indicating the significant difference between two morphological types (coiled and straight type). Based on the DNA molecular detection, the 24 strains of Dolichospermum were not cyanotoxin producers, but four strains of D. planctonicum and one strain of D. circinale showed to contain geosmin synthase gene. Such results not only presented the basic scientific information on biodiversity of bloom forming cyanobacteria and their ecological risk in Lake Zhelin, but also provided the basis on aquatic ecosystematic studies and protection along Lake Poyang watershed.