Role of Phylogenetic Structure in the Dynamics of Coastal Viral Assemblages.

Marine microbes, including viruses, are an essential part of the marine ecosystem, forming the base of the food web and driving biogeochemical cycles. Within this system, the composition of viral assemblages changes markedly with time, and some of these changes are repeatable through time; however, the extent to which these dynamics are reflected within versus among evolutionarily related groups of viruses is largely unexplored. To examine these dynamics, changes in the composition of two groups of ecologically important viruses and communities of their potential hosts were sampled every 2 weeks for 13 months at a coastal site in British Columbia, Canada. We sequenced two marker genes for viruses-the gene encoding the major capsid protein of T4-like phages and their relatives (gp23) and the RNA-dependent RNA polymerase (RdRp) gene of marnavirus-like RNA viruses-as well as marker genes for their bacterial and eukaryotic host communities, the genes encoding 16S rRNA and 18S rRNA. There were strong lagged correlations between viral diversity and community similarity of putative hosts, implying that the viruses influenced the composition of the host communities. The results showed that for both viral assemblages, the dominant clusters of phylogenetically related viruses shifted over time, and this was correlated with environmental changes. Viral clusters contained many ephemeral taxa and few persistent taxa, but within a viral assemblage, the ephemeral and persistent taxa were closely related, implying ecological dynamics within these clusters. Furthermore, these dynamics occurred in both the RNA and DNA viral assemblages surveyed, implying that this structure is common in natural viral assemblages.IMPORTANCE Viruses are major agents of microbial mortality in marine systems, yet little is known about changes in the composition of viral assemblages in relation to those of the microbial communities that they infect. Here, we sampled coastal seawater every 2 weeks for 1 year and used high-throughput sequencing of marker genes to follow changes in the composition of two groups of ecologically important viruses, as well as the communities of bacteria and protists that serve as their respective hosts. Different subsets of genetically related viruses dominated at different times. These results demonstrate that although the genetic composition of viral assemblages is highly dynamic temporally, for the most part the shuffling of genotypes occurs within a few clusters of phylogenetically related viruses. Thus, it appears that even in temperate coastal waters with large seasonal changes, the highly dynamic shuffling of viral genotypes occurs largely within a few subsets of related individuals.

Impact of a synthetic fungicide (fosetyl-Al and propamocarb-hydrochloride) and a biopesticide (Clonostachys rosea) on soil bacterial, fungal, and protist communities.

The use of synthetic pesticides in agriculture is increasingly debated. However, few studies have compared the impact of synthetic pesticides and alternative biopesticides on non-target soil microorganisms playing a central role in soil functioning. We conducted a mesocosm experiment and used high-throughput amplicon sequencing to test the impact of a fungal biopesticide and a synthetic fungicide on the diversity, the taxonomic and functional compositions, and co-occurrence patterns of soil bacterial, fungal and protist communities. Neither the synthetic pesticide nor the biopesticide had a significant effect on microbial α-diversity. However, both types of pesticides decreased the complexity of the soil microbial network. The two pesticides had contrasting impacts on the composition of microbial communities and the identity of key taxa as revealed by microbial network analyses. The biopesticide impacted keystone taxa that structured the soil microbial network. The synthetic pesticide modified biotic interactions favouring taxa that are less efficient at degrading organic compounds. This suggests that the biopesticides and the synthetic pesticide have different impact on soil functioning. Altogether, our study shows that pest management products may have functionally significant impacts on the soil microbiome even if microbial α-diversity is unaffected. It also illustrates the potential of high-throughput sequencing analyses to improve the ecotoxicological risk assessment of pesticides on non-target soil microorganisms.

RCy3: Network biology using Cytoscape from within R.

RCy3 is an R package in Bioconductor that communicates with Cytoscape via its REST API, providing access to the full feature set of Cytoscape from within the R programming environment. RCy3 has been redesigned to streamline its usage and future development as part of a broader Cytoscape Automation effort. Over 100 new functions have been added, including dozens of helper functions specifically for intuitive data overlay operations. Over 40 Cytoscape apps have implemented automation support so far, making hundreds of additional operations accessible via RCy3. Two-way conversion with networks from \textit{igraph} and \textit{graph} ensures interoperability with existing network biology workflows and dozens of other Bioconductor packages. These capabilities are demonstrated in a series of use cases involving public databases, enrichment analysis pipelines, shortest path algorithms and more. With RCy3, bioinformaticians will be able to quickly deliver reproducible network biology workflows as integrations of Cytoscape functions, complex custom analyses and other R packages.

High temporal and spatial diversity in marine RNA viruses implies that they have an important role in mortality and structuring plankton communities.

Viruses in the order Picornavirales infect eukaryotes, and are widely distributed in coastal waters. Amplicon deep-sequencing of the RNA dependent RNA polymerase (RdRp) revealed diverse and highly uneven communities of picorna-like viruses in the coastal waters of British Columbia (BC), Canada. Almost 300 000 pyrosequence reads revealed 145 operational taxonomic units (OTUs) based on 95% sequence similarity at the amino-acid level. Each sample had between 24 and 71 OTUs and there was little overlap among samples. Phylogenetic analysis revealed that some clades of OTUs were only found at one site; whereas, other clades included OTUs from all sites. Since most of these OTUs are likely from viruses that infect eukaryotic phytoplankton, and viral isolates infecting phytoplankton are strain-specific; each OTU probably arose from the lysis of a specific phytoplankton taxon. Moreover, the patchiness in OTU distribution, and the high turnover of viruses in the mixed layer, implies continuous infection and lysis by RNA viruses of a diverse array of eukaryotic phytoplankton taxa. Hence, these viruses are likely important elements structuring the phytoplankton community, and play a significant role in nutrient cycling and energy transfer.

The sensitivity of massively parallel sequencing for detecting candidate infectious agents associated with human tissue.

Massively parallel sequencing technology now provides the opportunity to sample the transcriptome of a given tissue comprehensively. Transcripts at only a few copies per cell are readily detectable, allowing the discovery of low abundance viral and bacterial transcripts in human tissue samples. Here we describe an approach for mining large sequence data sets for the presence of microbial sequences. Further, we demonstrate the sensitivity of this approach by sequencing human RNA-seq libraries spiked with decreasing amounts of an RNA-virus. At a modest depth of sequencing, viral transcripts can be detected at frequencies less than 1 in 1,000,000. With current sequencing platforms approaching outputs of one billion reads per run, this is a highly sensitive method for detecting putative infectious agents associated with human tissues.