广东省千灯湖拟柱孢藻(Cylindrospermopsis raciborskii)的形态和产毒能力的株间差异及系统进化

拟柱孢藻(Cylindrospermopsis raciborskii)是一种入侵蓝藻,能够产生拟柱孢藻毒素(cylindrospermopsin,CYN),严重危害人类健康.现有研究表明该藻已在我国广泛分布,更是华南地区常见的水华蓝藻,但目前对其产毒和起源还缺乏了解.本研究以中国广东省千灯湖分离出的10株拟柱孢藻为材料,对它们的生长、形态和产毒特性进行了观测,并构建了基于nif H和rpo C1基因的双基因系统进化树.结果表明,10株拟柱孢藻藻丝体形态均呈笔直型,除QDH1藻株外,其他的拟柱孢藻均可产生端生异形胞,厚壁孢子也常有出现;10藻株丝体的平均长度在41.0~77.7μm之间,宽度在2.433~3.125μm之间,它们的长宽比值差异显著.10藻株的比生长速率差异极显著,为0.075~0.174 d-1.检测发现10株藻中仅QDH7藻株可检测到6个CYN合成酶基因,液相色谱串联质谱法(LC-MS/MS)分析表明该藻株主要产生deoxy-CYN异构体,其浓度可达1745.19 ng/mL.系统进化分析表明千灯湖的拟柱孢藻与澳大利亚、欧洲和国内其他地区的藻株同源性较高,但基于rpo C1和nif H基因不能区分千灯湖的产毒藻株和非产毒藻株.本研究证实了广东省水体中存在产毒拟柱孢藻,需防范这类新型产毒蓝藻水华所带来的生态风险.

Intraspecific variation of morphological traits and toxin-producing capacity and phylogenetic analysis for Cylindrospermopsis raciborskii from Qiandenghu Lake, Guangdong Province

The invasive cyanobacterial species Cylindrospermopsis raciborskii is able to produce cylindrospermopsin(CYN)that cause serious damage to human health.The published studies have showed that C.raciborskii has been widely distributed in China,and appeared to be a common species in southern China.However,its origin and toxicity potential are still unknown.In this study,ten strains of C.raciborskii isolated from Qiandenghu Lake(QDH),Guangdong Province were used to observe their growth,morphology,toxin production and phylogeography based on nif H and rpo C1 genes.Our results showed that filaments of all C.raciborskii strains were straight.Apical heterocysts were observed in all C.raciborskii strains except the strain QDH1 and akinetes were also commonly appeared.The average filament length and width of ten strains ranged from 41.0 to 77.7μm and from 2.433 to 3.125μm,respectively,with a significant difference between strains.The specific growth rates of the 10 strains were also significantly different,ranging from 0.075 to 0.174 d-1.PCR analysis showed that only QDH7 gave positive amplification with six CYN synthesis genes.The strain was further analyzed by LC-MS/MS and confirmed to mainly produce deoxy-CYN isomer with the concentration of 1745.19 ng/mL.Phylogenetic analysis suggested that C.raciborskii from Qiandenghu Lake has high homology with the Australian,European and other Chinese strains,but the toxin-producing strains and non-toxin-producing strains in Qiandenghu Lake cannot be distinguished by rpo C1 and nif H genes.This study demonstrated the existence of CYN-producing C.raciborskii in water bodies of Guangdong Province,which highlights that it is necessary to prevent the ecological risks related to the newly emerging toxic cyanobacterial bloom.