Clasen Jessica L, Suttle Curtis A
Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
Appl Environ Microbiol. 2009 Feb;75(4):991-7. doi: 10.1128/AEM.02024-08. Epub 2008 Dec 16.
Viruses that infect phytoplankton are an important component of aquatic ecosystems, yet in lakes they remain largely unstudied. In order to investigate viruses (Phycodnaviridae) infecting eukaryotic phytoplankton in lakes and to estimate the number of potential host species, samples were collected from four lakes at the Experimental Lakes Area in Ontario, Canada, during the ice-free period (mid-May to mid-October) of 2004. From each lake, Phycodnaviridae DNA polymerase (pol) gene fragments were amplified using algal-virus-specific primers and separated by denaturing gradient gel electrophoresis; 20 bands were extracted from the gels and sequenced. Phylogenetic analysis indicated that freshwater environmental phycodnavirus sequences belong to distinct phylogenetic groups. An analysis of the genetic distances "within" and "between" monophyletic groups of phycodnavirus isolates indicated that DNA pol sequences that differed by more than 7% at the inferred amino acid level were from viruses that infect different host species. Application of this threshold to phylogenies of environmental sequences indicated that the DNA pol sequences from these lakes came from viruses that infect at least nine different phytoplankton species. A multivariate statistical analysis suggested that potential freshwater hosts included Mallomonas sp., Monoraphidium sp., and Cyclotella sp. This approach should help to unravel the relationships between viruses in the environment and the phytoplankton hosts they infect.
感染浮游植物的病毒是水生生态系统的重要组成部分，但在湖泊中它们仍 largely 未被研究。为了调查感染湖泊中真核浮游植物的病毒（藻病毒科）并估计潜在宿主物种的数量，于2004年无冰期（5月中旬至10月中旬）从加拿大安大略省实验湖区的四个湖泊采集了样本。从每个湖泊中，使用藻类病毒特异性引物扩增藻病毒科DNA聚合酶（pol）基因片段，并通过变性梯度凝胶电泳进行分离；从凝胶中提取20条带并进行测序。系统发育分析表明，淡水环境中的藻病毒序列属于不同的系统发育组。对藻病毒分离株的单系群“内部”和“之间”的遗传距离分析表明，在推断的氨基酸水平上差异超过7%的DNA pol序列来自感染不同宿主物种的病毒。将此阈值应用于环境序列的系统发育表明，这些湖泊中的DNA pol序列来自感染至少九种不同浮游植物物种的病毒。多变量统计分析表明，潜在的淡水宿主包括 Mallomonas sp.、Monoraphidium sp. 和 Cyclotella sp.。这种方法应有助于揭示环境中的病毒与其感染的浮游植物宿主之间的关系。
