Some biological and physicochemical properties of blue-green algal virus LPP-1

Patterns of virus growth across the diversity of life

Although viruses in their natural habitats add up to less than 10% of the biomass, they contribute more than 90% of the genome sequences [1]. These viral sequences or 'viromes' encode viruses that populate the Earth's oceans [2, 3] and terrestrial environments [4, 5], where their infections impact life across diverse ecological niches and scales [6, 7], including humans [8-10]. Most viruses have yet to be isolated and cultured [11-13], and surprisingly few efforts have explored what analysis of available data might reveal about their nature. Here, we compiled and analyzed seven decades of one-step growth and other data for viruses from six major families, including their infections of archaeal, bacterial and eukaryotic hosts [14-191]. We found that the use of host cell biomass for virus production was highest for archaea at 10%, followed by bacteria at 1% and eukarya at 0.01%, highlighting the degree to which viruses of archaea and bacteria exploit their host cells. For individual host cells, the yield of virus progeny spanned a relatively narrow range (10-1000 infectious particles per cell) compared with the million-fold difference in size between the smallest and largest cells. Furthermore, healthy and infected host cells were remarkably similar in the time they needed to multiply themselves or their virus progeny. Specifically, the doubling time of healthy cells and the delay time for virus release from infected cells were not only correlated (r = 0.71, p < 10-10, n = 101); they also spanned the same range from tens of minutes to about a week. These results have implications for better understanding the growth, spread and persistence of viruses in complex natural habitats that abound with diverse hosts, including humans and their associated microbes.

Host Traits Drive Viral Life Histories across Phytoplankton Viruses

Viruses are integral to ecological and evolutionary processes, but we have a poor understanding of what drives variation in key traits across diverse viruses. For lytic viruses, burst size, latent period, and genome size are primary characteristics controlling host-virus dynamics. Here we synthesize data on these traits for 75 strains of phytoplankton viruses, which play an important role in global biogeochemistry. We find that primary traits of the host (genome size, growth rate) explain 40%-50% of variation in burst size and latent period. Specifically, burst size and latent period both exhibit saturating relationships versus the host∶virus genome size ratio, with both traits increasing at low genome size ratios while showing no relationship at high size ratios. In addition, latent period declines as host growth rate increases. We analyze a model of latent period evolution to explore mechanisms that could cause these patterns. The model predicts that burst size may often be set by the host genomic resources available for viral construction, while latent period evolves to permit this maximal burst size, modulated by host metabolic rate. These results suggest that general mechanisms may underlie the evolution of diverse viruses. Future extensions of this work could help explain viral regulation of host populations, viral influence on community structure and diversity, and viral roles in biogeochemical cycles.

Cyanophages-viruses attacking blue-green algae

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Physiology and cytological chemistry blue-green algae

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Short-trichome mutant of Plectonema boryanum

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