Highly selective extermination of diatom blooms causing labor-discoloration by using habitual viruses.

在四年的研究中，成功地分离和鉴定了6种新的硅藻病毒(RsRNAV、CsNIV、CtenRNAV、CdebDNAV、CsfrRNAV、CcflDNAV)。所有病毒都是直径40 nm的二十面体病毒；它们的基因组要么是单链DNA，要么是单链RNA。单链RNA病毒的基因组是线性的，3‘-聚腺苷酸化；它们有两个开放阅读框架--一个复制酶多蛋白基因和一个结构多蛋白基因。它们与感染植物或昆虫的微小病毒有相当大的相似之处。另一方面，CsNIV和CcflDNAV基因组被认为是由一个共价闭合的环状单链DNA分子和一段线性单链DNA组成的。值得注意的是，在感染硅藻的病毒中发现了未知的基因组结构。根据BLAST搜索结果和RdRp结构域(RNA依赖的RNA聚合酶结构域)的系统发育分析，硅藻侵染的单链RNA和单链DNA病毒都是新的病毒组，与已知病毒只有非常远的亲缘关系，而且每个病毒组内的病毒之间存在显著的相似性。其中一些病毒在自然环境中以可检测到的水平存在(&gt；3.01传染病单位/毫升)，最高记录为3.1×10~(-4)传染病单位/毫升。这些数据表明病毒对自然硅藻种群有一定的影响。此外，通过实验室培养实验，通过病毒抑制共存硅藻的增殖，促进了紫菜的生长。这一结果将为开发防止紫菜变色的新方法提供基础数据。对这些感染硅藻的病毒的实际应用的进一步研究将是人们热切期待的。由于这一研究项目，成功地实现了硅藻学和病毒学的相遇。我们相信，由此产生的数据不仅从纯科学的角度来看是非常有价值的，而且从实用的应用科学的角度来看也是如此。

Within the four years research project, six novel diatom viruses(RsRNAV, CsNIV, CtenRNAV, CdebDNAV, CsfrRNAV, CcflDNAV) were successfully isolated and characterized. All are icosahedral viruses<40nm in diameter ; their genomes are either single-stranded DNA(ssDNA) or ssRNA. The genomes of the ssRNA viruses are linear and 3'-polyadenylated ; they have two open reading frames- a replicase polyprotein gene and a structural polyprotein gene. They showed considerable similarities to plant- or insect-infecting picomaviruses. On the other hand, CsNIV and CcflDNAV genomes are assumed to consist of a single molecule of covalently closed circular ssDNA as well as a segment of linear ssDNA. It is noticeable that the unknown genome structure was discovered in diatom-infecting viruses. Based on BLAST search results and phylogenetic analyses of RdRp domain(RNA-dependent RNA polymerase domain), both the diatom-infecting ssRNA and ssDNA viruses were shown to be novel virus groups that were only very distantly related with known viruses ; besides, significant similarities among viruses were observed within each virus group. Some of the viruses were shown to exist in natural environments at a detectable level(>3.01 infectious units/ml) ; the highest record was 3.1×10^4 infectious units/ml. These data suggest viruses have a certain impact on natural diatom populations. Furthermore, through a laboratory culture experiment, growth of laver was improved by virally inhibiting coexisting diatom proliferation. This result will provide basic data for developing a new method to prevent laver from discoloration. Further study on practical use of these diatom-infecting viruses will be eagerly expected. Due to this research project, encounter between diatomology and virology was successfully realized. We believe that the resultant data are of great value not only from the viewpoint of pure science but also practical applied science.