Prasinovirus distribution in the Northwest Mediterranean Sea is affected by the environment and particularly by phosphate availability

Abstract

Numerous seawater lagoons punctuate the southern coastline of France. Exchanges of seawater between these lagoons and the open sea are limited by narrow channels connecting them. Lagoon salinities vary according to evaporation and to the volume of freshwater arriving from influent streams, whose nutrients also promote the growth of algae. We compared Prasinovirus communities, whose replication is supported by microscopic green algae, in four lagoons and at a coastal sampling site. Using high-throughput sequencing of DNA from a giant virus-specific marker gene, we show that the environmental conditions significantly affect the types of detectable viruses across samples. In spatial comparisons between 5 different sampling sites, higher levels of phosphates, nitrates, nitrites, ammonium and silicates tend to increase viral community richness independently of geographical distances between the sampling sites. Finally, comparisons of Prasinovirus communities at 2 sampling sites over a period of 10 months highlighted seasonal effects and the preponderant nature of phosphate concentrations in constraining viral distribution.

A Viral Immunity Chromosome in the Marine Picoeukaryote, Ostreococcus tauri

“…tauri population in coastal north-western Mediterranean Sea [17]. These waters are indeed infested with prasinoviruses [84], and prasinoviruses are similarly abundant in the English Channel, where they infect Micromonas spp. [85].…”

Diversity of Viruses Infecting the Green Microalga Ostreococcus lucimarinus

“…Multiple independent pho4 gene transfer events (with retention) have been proposed to occur between marine viruses and their hosts. Thus, manipulation of host phosphate uptake may be an important adaptation for viral proliferation in marine systems, although it is not necessarily an indicator of low ambient phosphate concentrations (10,54,58). Methyltransferase genes also are found frequently in viral genomes, where they protect the viral genome against degradation and/or might modify the host genome (59).…”

“…Comparisons and extrapolations from marine metaviromes indicate that at least for phages, viral genetic distance between two distinct geographical locations is never high enough to detect site-specific viral populations, whatever the geographical location (3,7). However, metagenomics and taxonomic markerbased studies relying on deeper sequencing show that at least a partial biogeography of viral populations can be detected (5,6,(8)(9)(10). Thus, both the existence of a common core set of virus communities and distinct biogeographic patterns have been reported.…”

Variation in the Genetic Repertoire of Viruses Infecting Micromonas pusilla Reflects Horizontal Gene Transfer and Links to Their Environmental Distribution

“…This is less stringent than Short and Short [23], who clustered the nucleotide level at 97% and Bellec et al [35] who considered differences by single nucleotides as defining a distinct Ostreococcus virus haplotype. In contrast, it is more stringent than clustering at 75% identity, which was used in another study on prasinovirus distribution [36]. Overall, the identity level used in this study is appropriate to approximate the similarity and difference in gene content of viruses in environmental samples.…”

“…Furthermore, the diversity and composition of prasinovirus communities is influenced by environmental factors, particularly the availability of phosphate [36]. A recent study on cyanophage isolates, which prominently host a range of AMGs, linked their genome similarity with environmental distribution, thus formulating a diversification of viruses into ecotypes [34].…”