Surface microlayer-mediated virome dissemination in the Central Arctic.

Background: Aquatic viruses act as key players in shaping microbial communities. In polar environments, they face significant challenges such as limited host availability and harsh conditions. However, due to the restricted accessibility of these ecosystems, our understanding of viral diversity, abundance, adaptations, and host interactions remains limited.

Ecogenomics and cultivation reveal distinctive viral-bacterial communities in the surface microlayer of a Baltic Sea slick.

Visible surface films, termed slicks, can extensively cover freshwater and marine ecosystems, with coastal regions being particularly susceptible to their presence. The sea-surface microlayer (SML), the upper 1-mm at the air-water interface in slicks (herein slick SML) harbors a distinctive bacterial community, but generally little is known about SML viruses. Using flow cytometry, metagenomics, and cultivation, we characterized viruses and bacteria in a brackish slick SML in comparison to non-slick SML as well as seawater below slick and non-slick areas (subsurface water = SSW).

Four additional natural 7-deazaguanine derivatives in phages and how to make them.

Bacteriophages and bacteria are engaged in a constant arms race, continually evolving new molecular tools to survive one another. To protect their genomic DNA from restriction enzymes, the most common bacterial defence systems, double-stranded DNA phages have evolved complex modifications that affect all four bases. This study focuses on modifications at position 7 of guanines.

Nutrient driven transcriptional changes during phage infection in an aquatic Gammaproteobacterium.

Phages modulate bacterial metabolism during infection by regulating gene expression, which influences aquatic nutrient cycling. However, the effects of shifting nutrient regimes are less understood. Here, we analyzed transcriptomes of an ecologically relevant Gammaproteobacterium and its lytic phage in high (HNM) and low (LNM) nutrient medium.

Dynamics of Baltic Sea phages driven by environmental changes.

Phage predation constitutes a major mortality factor for bacteria in aquatic ecosystems, and thus, directly impacts nutrient cycling and microbial community dynamics. Yet, the population dynamics of specific phages across time scales from days to months remain largely unexplored, which limits our understanding of their influence on microbial succession. To investigate temporal changes in diversity and abundance of phages infecting particular host strains, we isolated 121 phage strains that infected three bacterial hosts during a Baltic Sea mesocosm experiment.

Phage Biocontrol of in Water.

Bacteriophage control of harmful or pathogenic bacteria has aroused growing interest, largely due to the rise of antibiotic resistance. The objective of this study was to test phages as potential agents for the biocontrol of an opportunistic pathogen in water. Two bacteriophages (vB_PaeM_V523 and vB_PaeM_V524) were isolated from wastewater and characterized physically and functionally.

Viruses of Microbes 2020: The Latest Conquest on Viruses of Microbes.

This Special Issue celebrates viruses of microbes: those viruses that infect archaea, bacteria and microbial eukaryotes [...

Cyanophage Diversity and Community Structure in Dead Zone Sediments.

Up to 20% of prokaryotic organisms in the oceans are estimated to die every day due to viral infection and lysis. Viruses can therefore alter microbial diversity, community structure, and biogeochemical processes driven by these organisms. Cyanophages are viruses that infect and lyse cyanobacterial cells, adding bioavailable carbon and nutrients into the environment.

The Fennoscandian Shield deep terrestrial virosphere suggests slow motion 'boom and burst' cycles.

The deep biosphere contains members from all three domains of life along with viruses. Here we investigate the deep terrestrial virosphere by sequencing community nucleic acids from three groundwaters of contrasting chemistries, origins, and ages. These viromes constitute a highly unique community compared to other environmental viromes and sequenced viral isolates.

Structure and function of virion RNA polymerase of a crAss-like phage.

CrAss-like phages are a recently described expansive group of viruses that includes the most abundant virus in the human gut. The genomes of all crAss-like phages encode a large virion-packaged protein that contains a DFDxD sequence motif, which forms the catalytic site in cellular multisubunit RNA polymerases (RNAPs). Here, using Cellulophaga baltica crAss-like phage phi14:2 as a model system, we show that this protein is a DNA-dependent RNAP that is translocated into the host cell along with the phage DNA and transcribes early phage genes.

Diversity and Host Interactions Among Virulent and Temperate Baltic Sea Phages.

Viruses in aquatic environments play a key role in microbial population dynamics and nutrient cycling. In particular, bacteria of the phylum are known to participate in recycling algal blooms. Studies of phage-host interactions involving this phylum are hence important to understand the processes shaping bacterial and viral communities in the ocean as well as nutrient cycling.

Non-host class II ribonucleotide reductase in Thermus viruses: sequence adaptation and host interaction.

Ribonucleotide reductases (RNR) are essential enzymes for all known life forms. Their current taxonomic distribution suggests extensive horizontal gene transfer e.g.

Metatranscriptomes Reveal That All Three Domains of Life Are Active but Are Dominated by Bacteria in the Fennoscandian Crystalline Granitic Continental Deep Biosphere.

The continental subsurface is suggested to contain a significant part of the earth's total biomass. However, due to the difficulty of sampling, the deep subsurface is still one of the least understood ecosystems. Therefore, microorganisms inhabiting this environment might profoundly influence the global nutrient and energy cycles.

Genomic Characterization of Cyanophage vB_AphaS-CL131 Infecting Filamentous Diazotrophic Cyanobacterium Reveals Novel Insights into Virus-Bacterium Interactions.

While filamentous cyanobacteria play a crucial role in food web dynamics and biogeochemical cycling of many aquatic ecosystems around the globe, the knowledge regarding the phages infecting them is limited. Here, we describe the complete genome of the virulent cyanophage vB_AphaS-CL131 (here, CL 131), a phage that infects the filamentous diazotrophic bloom-forming cyanobacterium in the brackish Baltic Sea. CL 131 features a 112,793-bp double-stranded DNA (dsDNA) genome encompassing 149 putative open reading frames (ORFs), of which the majority (86%) lack sequence homology to genes with known functions in other bacteriophages or bacteria.

Insights into cyanophage-mediated dynamics of nodularin and other non-ribosomal peptides in Nodularia spumigena.

The effect of cyanophage infection and lysis on the dynamics of the hepatotoxin nodularin (NOD) and other non-ribosomal peptides (NRPs) produced by cyanobacteria is poorly understood. In this study, changes in concentration of NOD and other NRPs during cyanophage infection of the filamentous cyanobacteria Nodularia spumigena were assessed using incubation experiments. Viral infection and lysis were associated with a significant reduction (93% at the 96 h post infection) of N.

Regulation of infection efficiency in a globally abundant marine Bacteriodetes virus.

This corrects the article DOI: 10.1038/ismej.2016.

Large-scale maps of variable infection efficiencies in aquatic Bacteroidetes phage-host model systems.

Microbes drive ecosystem functioning and their viruses modulate these impacts through mortality, gene transfer and metabolic reprogramming. Despite the importance of virus-host interactions and likely variable infection efficiencies of individual phages across hosts, such variability is seldom quantified. Here, we quantify infection efficiencies of 38 phages against 19 host strains in aquatic Cellulophaga (Bacteroidetes) phage-host model systems.

Regulation of infection efficiency in a globally abundant marine Bacteriodetes virus.

Bacteria impact humans, industry and nature, but do so under viral constraints. Problematically, knowledge of viral infection efficiencies and outcomes derives from few model systems that over-represent efficient lytic infections and under-represent virus-host natural diversity. Here we sought to understand infection efficiency regulation in an emerging environmental Bacteroidetes-virus model system with markedly different outcomes on two genetically and physiologically nearly identical host strains.

Microbial metagenomes from three aquifers in the Fennoscandian shield terrestrial deep biosphere reveal metabolic partitioning among populations.

Microorganisms in the terrestrial deep biosphere host up to 20% of the earth's biomass and are suggested to be sustained by the gases hydrogen and carbon dioxide. A metagenome analysis of three deep subsurface water types of contrasting age (from <20 to several thousand years) and depth (171 to 448 m) revealed phylogenetically distinct microbial community subsets that either passed or were retained by a 0.22 μm filter.

Life-style and genome structure of marine Pseudoalteromonas siphovirus B8b isolated from the northwestern Mediterranean Sea.

Marine viruses (phages) alter bacterial diversity and evolution with impacts on marine biogeochemical cycles, and yet few well-developed model systems limit opportunities for hypothesis testing. Here we isolate phage B8b from the Mediterranean Sea using Pseudoalteromonas sp. QC-44 as a host and characterize it using myriad techniques.

Contrasting genomic patterns and infection strategies of two co-existing Bacteroidetes podovirus genera.

Bacterial viruses (phages) are abundant, ecologically important biological entities. However, our understanding of their impact is limited by model systems that are primarily not well represented in nature, e.g.

Twelve previously unknown phage genera are ubiquitous in global oceans.

Viruses are fundamental to ecosystems ranging from oceans to humans, yet our ability to study them is bottlenecked by the lack of ecologically relevant isolates, resulting in "unknowns" dominating culture-independent surveys. Here we present genomes from 31 phages infecting multiple strains of the aquatic bacterium Cellulophaga baltica (Bacteroidetes) to provide data for an underrepresented and environmentally abundant bacterial lineage. Comparative genomics delineated 12 phage groups that (i) each represent a new genus, and (ii) represent one novel and four well-known viral families.

Cultivated single-stranded DNA phages that infect marine Bacteroidetes prove difficult to detect with DNA-binding stains.

This is the first description of cultivated icosahedral single-stranded DNA (ssDNA) phages isolated on heterotrophic marine bacterioplankton and with Bacteroidetes hosts. None of the 8 phages stained well with DNA-binding stains, suggesting that in situ abundances of ssDNA phages are drastically underestimated using conventional methods for enumeration.

Virus production and lysate recycling in different sub-basins of the northern Baltic Sea.

In the Gulf of Bothnia, northern Baltic Sea, a large freshwater inflow creates north-southerly gradients in physico-chemical and biological factors across the two sub-basins, the Bothnian Bay (BB) and the Bothnian Sea. In particular, the sub-basins differ in nutrient limitation (nitrogen vs. phosphorus; P).

Bacteriophages drive strain diversification in a marine Flavobacterium: implications for phage resistance and physiological properties.

Genetic, structural and physiological differences between strains of the marine bacterium Cellulophaga baltica MM#3 (Flavobacteriaceae) developing in response to the activity of two virulent bacteriophages, Phi S(M) and Phi S(T), was investigated during 3 weeks incubation in chemostat cultures. A distinct strain succession towards increased phage resistance and a diversification of the metabolic properties was observed. During the incubation the bacterial population diversified from a single strain, which was sensitive to 24 tested Cellulophaga phages, into a multistrain and multiresistant population, where the dominant strains had lost susceptibility to up to 22 of the tested phages.