Kimura-Sakai S, Sako Y, Yoshida T
Laboratory of Marine Microbiology, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
Lett Appl Microbiol. 2015 Apr;60(4):400-8. doi: 10.1111/lam.12387. Epub 2015 Feb 18.
Microcystis aeruginosa forms toxic cyanobacterial blooms throughout the world where its infectious phages are thought to influence host population dynamics. To assess the cyanophage impact on the host dynamics, we previously monitored Ma-LMM01-type phage abundance using a real-time PCR with a primer set designed based on the sequence of Microcystis phage Ma-LMM01; and we estimated the phage-infected host cell abundance. However, a recent study shows the Ma-LMM01 g91 gene sequence belongs to the smallest group, group III, of the three genotype groups, suggesting Ma-LMM01-type phage abundance was underestimated. Therefore, to re-evaluate the effect of Ma-LMM01-type phages on their hosts, we monitored the abundance of Ma-LMM01-type phages using real-time PCR with a new primer set designed based on the sequences of genotype groups I-III. We found phage abundance between 10(3) and 10(4) ml(-1) using the new primer set in samples where previously these phages were not detected using the old primer set. The frequency of Ma-LMM01-type phage-infected cells to Ma-LMM01-type phage-susceptible host cells may be as high as 30%, suggesting the phages may occasionally affect not only shifts in the genetic composition but also the dynamics of Ma-LMM01-type phage-susceptible host populations.
Phages are one of the factors that may control the ecology of their host blooms. Therefore, it is essential to estimate phage abundance to understand phage impact on host populations. A real-time PCR assay was improved to detect a larger range of Microcystis cyanophages in natural surroundings where no phages were detected using a previous method by re-designing a new primer set based on sequences from three Ma-LMM01-type phage genetic groups. The new method allows us to determine the distribution, dynamics and infection cycle of the phage to help understand the interaction between the phages and the hosts.
铜绿微囊藻在世界各地形成有毒蓝藻水华，其感染性噬菌体被认为会影响宿主种群动态。为了评估噬藻体对宿主动态的影响，我们之前使用基于微囊藻噬菌体Ma-LMM01序列设计的引物对，通过实时PCR监测Ma-LMM01型噬菌体丰度；并估计了被噬菌体感染的宿主细胞丰度。然而，最近的一项研究表明，Ma-LMM01 g91基因序列属于三个基因型组中最小的组，即III组，这表明Ma-LMM01型噬菌体丰度被低估了。因此，为了重新评估Ma-LMM01型噬菌体对其宿主的影响，我们使用基于I-III基因型组序列设计的新引物对，通过实时PCR监测Ma-LMM01型噬菌体的丰度。我们发现，在之前使用旧引物对未检测到这些噬菌体的样本中，使用新引物对检测到噬菌体丰度在10³至10⁴ ml⁻¹之间。Ma-LMM01型噬菌体感染细胞与Ma-LMM01型噬菌体敏感宿主细胞的频率可能高达30%，这表明噬菌体可能偶尔不仅会影响遗传组成的变化，还会影响Ma-LMM01型噬菌体敏感宿主种群的动态。
噬菌体是可能控制其宿主水华生态的因素之一。因此，估计噬菌体丰度对于了解噬菌体对宿主种群的影响至关重要。通过基于三个Ma-LMM01型噬菌体基因组序列重新设计新引物对，改进了实时PCR检测方法，以在自然环境中检测到更大范围的微囊藻噬藻体，而之前的方法未检测到这些噬菌体。新方法使我们能够确定噬菌体的分布、动态和感染周期，以帮助理解噬菌体与宿主之间的相互作用。
