新型聚球藻噬藻体Yong-L2-223的分离及基因组分析  

Isolation and genome analysis of a novel Synechococcus cyanophage Yong-L2-223

作　　者：胡嘉琪 潘灵婷 周钦 钱敏桦 蔡汝倩 王飞 任晓清 林威 李登峰[1] 童贻刚 HU Jiaqi;PAN Lingting;ZHOU Qin;QIAN Minhua;CAI Ruqian;WANG Fei;REN Xiaoqing;LIN Wei;LI Dengfeng;TONG Yigang(School of Marine Sciences,Ningbo University,Ningbo 315000,Zhejiang,China;College of Life Science and Technology,Beijing University of Chemical Technology,Beijing 100029,China)

机构地区：[1]宁波大学海洋学院,浙江宁波315000 [2]北京化工大学生命科学与技术学院,北京100029

出　　处：《微生物学报》2024年第1期189-207,共19页Acta Microbiologica Sinica

基　　金：国家重点研发计划(2018YFA0903000);宁波市重点研发计划(2022Z170)。

摘　　要：【目的】噬藻体(cyanophages)是特异性侵染蓝藻(cyanobacteria)的病毒,广泛分布于各类水体中,在调节蓝藻种群动态和密度、推动生物地球水生生态系统循环中起着重要作用。本研究的目的在于分离、鉴定噬藻体。【方法】本研究以海洋聚球藻(Synechococcus sp.)PCC 7002为指示宿主,从淡水水样中分离培养一株新型噬藻体Yong-L2-223,对其进行了宿主范围实验、全基因组测序、基因功能注释和系统进化分析。【结果】针对31株供试蓝藻的宿主范围实验,结果除指示藻PCC 7002[属于聚球藻目(Synechococcales)]外,Yong-L2-223能够感染2株淡水蓝藻,分别是来源于滇池的绿色微囊藻(Microcystis viridis)FACHB-1342[属于色球藻目(Chroococcales)]和水华束丝藻(Aphanizomenon flos-aquae)FACHB-1209[属于念珠藻目(Nostocales)]。既可在高盐条件下感染海洋蓝藻,又可在低盐条件下感染淡水蓝藻,Yong-L2-223具有广盐性。透射电镜观察表明,Yong-L2-223呈肌尾病毒样(myovirus-like),头部直径约60nm,尾部长约136nm。Yong-L2-223的双链DNA基因组全长为65725bp,G+C含量为58.6%,含有100个开放阅读框(openreading frame,ORFs)。Yong-L2-223基因组中含有编码Cas4、基因转移因子(gene transfer factor,GTA)的基因,含有辅助代谢基因(auxiliary metabolic genes,AMGs),含有pre-Q0生物合成基因簇(gene cluster)。这些基因的编码产物可能有助于该噬藻体对宿主的适应、感染,从而实现跨3个目(order)感染蓝藻。将Yong-L2-223基因组与现有数据库中所有病毒基因组进行序列配对比较(pairwise sequence comparison,PASC),结果最高PASC值仅为3.78%,远远低于国际病毒分类委员会(International Committee on Taxonomy of Viruses,ICTV)界定属的边界值(70%)。在基于全基因组的蛋白谱系统进化树中,Yong-L2-223形成一个独立的分支(branch),与其他病毒间进化距离远。【结论】Yong-L2-223在有尾纲中代表一个新的未知的属。本研究首次[Objective]Cyanophages,the viruses specifically infecting cyanobacteria,are ubiquitous in water environments.They play a role in regulating the population dynamics and density of cyanobacteria and promote the biogeochemical cycling of the aquatic ecosystem.This study aims to isolate and identify a cyanophage.[Methods]A novel cyanophage Yong-L2-223 was isolated from fresh water samples with marine Synechococcus sp.PCC 7002 as the indicator host.The host range,genome sequence,open reading frames(ORFs),and phylogenetic relationship of Yong-L2-223 were studied.[Results]The host range tests against 31 strains of cyanobacteria showed that Yong-L2-223 could infect the indicator host PCC 7002(Synechococcales)and two freshwater strains Microcystis viridis FACHB-1342(Chroococcales)and Aphanizomenon flos-aquae FACHB-1209(Nostocales)from the Dianchi Lake.The infection of the cyanobacterial strains from both the seawater and freshwater samples indicated that Yong-L2-223 was a euryhaline cyanophage.Yong-L2-223 was myovirus-like,consisting of an icosahedral head(about 60 nm in diameter)and a contractile tail(about 136 nm in length).The genome(double-stranded DNA)of Yong-L2-223 had a length of 65725 bp,with the G+C content of 58.6% and 100 ORFs.It was predicted to carry the Cas4 gene,gene transfer factor(GTA)gene,auxiliary metabolic genes(AMGs),and a gene cluster for the synthesis of pre-Q0.These genes may contribute to the adaptation and infection of the cyanophage in cyanobacteria of three orders.The pairwise sequence comparison(PASC)illustrated that the highest similarity sharing by cyanophage Yong-L2-223 and all the viruses in the current genome databases was only 3.78%,far below the genus boundary cut-off of 70% defined by the International Committee on Taxonomy of Viruses.In the phylogenetic tree based on the whole proteomes,Yong-L2-223 formed an independent branch,with long evolutionary distances from other phages.[Conclusion]Yong-L2-223 is a new genus of the Caudoviricetes class.For the first time,we used a marine cyanob

关 键 词：海洋聚球藻 淡水噬藻体 基因组分析 

分 类 号：X55[环境科学与工程—环境工程] Q933[生物学—微生物学]