Dataset Information

Diurnal infection patterns and impact of Microcystis cyanophages in a Japanese pond.

ABSTRACT: Viruses play important roles in regulating the abundance, clonal diversity, and composition of their host populations. To assess their impact on the host populations, it is essential to understand the dynamics of virus infections in the natural environment. Cyanophages often carry host-like genes, including photosynthesis genes, which maintain host photosynthesis. This implies a diurnal pattern of cyanophage infection depending on photosynthesis. Here we investigated the infection pattern of Microcystis cyanophage by following the abundances of the Ma-LMM01-type phage tail sheath gene g91 and its transcript in a natural population. The relative g91 mRNA abundance within host cells showed a peak during the daylight hours and was lowest around midnight. The phage g91 DNA copy numbers in host cell fractions, which are predicted to indicate phage replication, increased in the afternoon, followed by an increase in the free-phage fractions. In all fractions, at least 1 of 71 g91 genotypes was observed (in tested host cell, free-phage, and RNA fractions), indicating that the replication cycle of the cyanophage (i.e., injection, transcription, replication, and release of progeny phages) was occurring. Thus, Microcystis cyanophage infection occurs in a diel cycle, which may depend on the light cycle. Additionally, our data show that the abundance of mature cyanophage produced within host cells was 1 to 2 orders of magnitude greater than that of released phages, suggesting that phage production may be higher than previously reported.

SUBMITTER: Kimura S

PROVIDER: S-EPMC3406124 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Diurnal infection patterns and impact of Microcystis cyanophages in a Japanese pond.

Kimura Shigeko S Yoshida Takashi T Hosoda Naohiko N Honda Takashi T Kuno Sotaro S Kamiji Rikae R Hashimoto Ryoya R Sako Yoshihiko Y

Applied and environmental microbiology 20120608 16

Viruses play important roles in regulating the abundance, clonal diversity, and composition of their host populations. To assess their impact on the host populations, it is essential to understand the dynamics of virus infections in the natural environment. Cyanophages often carry host-like genes, including photosynthesis genes, which maintain host photosynthesis. This implies a diurnal pattern of cyanophage infection depending on photosynthesis. Here we investigated the infection pattern of Mic ...[more]

PMID: 22685141

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Project description:The freshwater cyanobacterium Microcystis aeruginosa frequently forms toxic massive blooms and exists in an arms race with its infectious phages in aquatic natural environments, and as a result, has evolved extremely diverse and elaborate antiviral defense systems, including the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated genes (Cas) system. Here, to assess Microcystis population dynamics associated with exogenous mobile genetic elements such as phages and plasmids, we examined the temporal variation in CRISPR genotypes (CTs) by analyzing spacer sequences detected in a natural pond between June and October 2013 when a cyanobacterial bloom occurred. A total of 463,954 high-quality leader-end CRISPR sequences were obtained and the sequences containing spacers were classified into 31 previously reported CTs and 68 new CTs based on the shared order of the leader-end spacers. CT19 was the most dominant genotype (32%) among the 16 most common CTs, followed by CT52 (14%) and CT58 (9%). Spacer repertoires of CT19 showed mainly two different types; CT19origin, which was identical to the CT19 spacer repertoire of previously isolated strains, and CT19new+, which contained a new spacer at the leader-end of the CRISPR region of CT19origin, which were present in almost equal abundance, accounting for up to 99.94% of CT19 sequences. Surprisingly, we observed the spacer repertoires of the second to tenth spacers of CT19origin at the most leader-end of proto-genotype sequences of CT19origin. These were observed during the sampling in this study and our previous study at the same ecosystem in 2010 and 2011, suggesting these CTs persisted from 2011 to 2013 in spite of phage pressure. The leader-end variants were observed in other CT genotypes. These findings indicated an incomplete selective sweep of Microcystis populations. We explained the phenomenon as follow; the abundance of Microcystis varied seasonally and drastically, resulting that Microcystis populations experience a bottleneck once a year, and thereby founder effects following a bottleneck mean that older CTs have an equal chance of increasing in prevalence as the CTs generated following acquisition of newer spacers.

Dataset Information

Diurnal infection patterns and impact of Microcystis cyanophages in a Japanese pond.

Publications

Diurnal infection patterns and impact of Microcystis cyanophages in a Japanese pond.

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