Viruses are the most abundant, diverse, and widespread known biological entities in aquatic systems. Viruses infect a diverse range of organisms, from bacteria to whales, and their impacts on aquatic ecosystems extend beyond causing mortality and disease. Viral infections play a crucial role in shaping biogeochemical cycles, facilitating gene transfer, and altering metabolic processes of host cells. Ecologically, viruses have different lifestyles that exist on a continuum between horizontal and vertical transmission (e.g., spanning lysis to lysogeny) – and they also differ in host specificity – leading to questions of how coexistence is mediated and what conditions favor particular virus life-history strategies. Additionally, ongoing research is needed to better understand the factors regulating virus-host interactions and how these interactions vary across different spatial and temporal scales. Biogeochemically, in marine systems viral-induced lysis is hypothesized: (a) to enhance microbial mediated respiration and nutrient recycling in the microbial loop via the release of labile nutrients retained in surface waters – the viral shunt; and also (b) to increase particle aggregation and export to the deep oceans – the viral shuttle. The large-scale biogeochemical impacts of small, yet abundant viruses in aquatic systems remains open to investigation. While new technologies have advanced the roles of viruses in aquatic ecology and biogeochemistry over the last three decades, identifying and quantifying the importance of virus-mediated processes and how they scale up across differing aquatic ecosystems remains challenging. We invite submissions focusing on the analysis of field sampling, experimental systems, theory, modeling, and/or bioinformatics approaches. We encourage interdisciplinary submissions that integrate multiple lines of evidence and those which seek to quantify rates and processes. Topics of interest include the regulation of virus-host interactions, biophysical interactions, mortality rates and population dynamics, the influence on aquatic food web functioning and biogeochemical cycling, novel host-virus systems, and other studies that advance our understanding of the vast roles that viruses play in aquatic ecosystems.
Lead Organizer: Stephen Beckett, University of Maryland (beckett@umd.edu)
Co-organizers:
Elaine Luo, University of North Carolina at Charlotte (elaine.luo@charlotte.edu)
Kristina Mojica, University of Southern Mississippi (Kristina.Mojica@usm.edu)
Presentations
06:00 PM
Can viral induced mortality be represented with a quadratic mortality function? (8959)
Primary Presenter: Eric Carr, University of Tennessee (ecarr@utk.edu)
The impact of viral induced mortality of algal and bacterial cells on elemental flow has been poorly quantified. Biogeochemical modelers have avoided explicitly resolving viral infection by assuming that phytoplankton mortality increases quadratically with cell density. Using a water-column model with a nutrient-phytoplankton-zooplankton-virus-detritus (NPZVD) configuration including an infected phytoplankton class, we ask whether the quadratic mortality function captures patterns of viral induced mortality. The quadratic function underpredicts viral mortality during shallow mixing when phytoplankton biomass is highest, and overpredicts mortality during deep mixing and beneath the mixed layer when phytoplankton biomass is lowest. We interpret these findings to be associated with the time-delay that arises between initial infection and host lysis, that requires an explicit representation of infected cells. We present initial assessments of the magnitude of error associated with quadratic mortality on integrated primary production and carbon export and discuss the implications of our findings for large-scale models of ocean biogeochemistry.
06:00 PM
EPISOMAL VIRUS MAINTENANCE ENABLES BACTERIAL POPULATION RECOVERY FROM INFECTION AND VIRUS-BACTERIAL COEXISTENCE (8926)
Primary Presenter: AKASH ARANI, University of Maryland (aarani@umd.edu)
Hypersaline environments harbor the highest concentrations of virus-like particles (VLPs) reported for aquatic ecosystems. The substantial densities of both microbial populations and VLPs challenge traditional explanations of top-down control exerted by viruses. At close to saturation salinities, prokaryotic populations are dominated by Archaea and the bacterial clade Salinibacter. In this work we examine the episomal maintenance of a virus within a Salinibacter ruber host. We found that infected cultures of Sal. ruber M1 developed a population-level resistance and underwent systematic and reproducible recovery post infection that was counter-intuitively dependent on the multiplicity of infection (MOI), where higher MOI led to better host outcomes. Furthermore, we developed a nonlinear population dynamics model that successfully reproduced the qualitative features of the recovery. The success of the model suggests that the maintenance of the virus episomally, often referred to as pseudolysogeny, and lysis inhibition allow for host-virus co-existence under high MOI infections. Our results emphasize the ecological importance of exploring a spectrum of viral infection strategies beyond the conventional binary of lysis or lysogeny.
06:00 PM
Genomics of environmental microcompartments reveals novel viruses and other genetic elements in the ocean (9647)
Primary Presenter: Ramunas Stepanauskas, Bigelow Laboratory for Ocean Sciences (rstepanauskas@bigelow.org)
Viruses and other extracellular genetic elements constitute a major fraction of marine DNA and play important roles in plankton ecology and evolution, but their composition remains challenging to decipher. Here, we report a novel technology that involves compartmentalization of natural samples into picolitre-sized semipermeable capsules (SPCs) and subsequent amplification, barcoding and sequencing of DNA from individual SPCs. Our workflow enabled quantitative de novo assemblies of thousands of single-amplified genomes (SAGs) from the SPCs of a single experiment, capturing a broad range of both cellular and extracellular entities. The technology was successfully applied on surface and deep ocean water samples and on marine sediments. Over 2,000 SPC SAG genomes were sequenced from a 250nL sample of surface seawater. The obtained 11:1 virus-to-cell ratio, the predominance of Caudoviricetes, and the taxonomy of cellular SAG assemblies were in good agreement with the current knowledge of marine plankton composition. Genomes of a substantial fraction of viral SAGs were similar to the dUTP-containing Naomiviridae and lacked matches in a metagenome from the same sample, indicating their use of non-canonical DNA (e.g. not A, T, C and G). The reported Environment Micro-Compartment Genomics (EMCG) technology offers transformative opportunities for unbiased and cost-effective studies of individual viruses and other genetic elements in nature.
06:00 PM
TEMPERATURE CORRELATES WITH PHAGE RESISTANCE IN MICROCYSTIS AERUGINOSA NIES298 (9244)
Primary Presenter: Kennedi Hambrick, University of Tennessee (khambri3@vols.utk.edu)
Microcystis aeruginosa is a freshwater cyanobacterium largely recognized for its role in the formation of harmful algal blooms (HABs). However, less well characterized are the host-phage interactions that occur in these toxic blooms. Here, we describe the relationship between a microcystin producing strain of M. aeruginosa, NIES298, and its lytic phage Ma-LMM01. In this study we explored how host pre-acclimation to different temperature conditions, which also affect toxin production in NIES298, influenced sensitivity to subsequent infection by Ma-LMM01. NIES298 cultures pre-acclimated to 26° C (7.15 +/- 0.02 fg cell-1 toxin) were completely lysed whether infection occurred at 26° C or at 19° C. In contrast, 19° C acclimated NIES298 (14.13 +/- 0.20 fg cell-1 toxin) resisted lytic infection regardless of infection temperature. To investigate key parameters driving these dynamics, a mathematical model was formulated which indicated a partially resistant subpopulation of comparable abundance in both 19° C and 26° C acclimated hosts. Specifically, we found the 19° C acclimated host subpopulation was almost completely resistant to infection, while the 26° C acclimated host subpopulation was only partially resistant. Overall, our observations demonstrate that NIES298 acclimation to a decrease in temperature played a role in the development / selection of resistance to Ma-LMM01. Ongoing efforts to better elucidate the mechanism of resistance to infection include examinations of the potential role of microcystin, whose intracellular concentration at 26° C was half that at 19° C.
06:00 PM
Towards trait-based modeling of aquatic viral ecology (9068)
Primary Presenter: Stephen Beckett, University of Maryland (beckett@umd.edu)
Viruses are highly abundant in aquatic ecosystems and are expected to play important roles in top-down regulation of microbial prey, as well as in biogeochemical cycling via enhanced nutrient recycling (viral shunt) and enhanced export from surface waters (viral shuttle). Yet, evaluating such impacts within global biogeochemical models remains elusive. Here, we explore how trait-based modeling approaches used to represent phytoplankton dynamics can be adapted to studies of aquatic viral ecology. We present examples of fitting mechanistic ecological models to data as a means to estimate relevant viral life-history traits such as adsorption rates and burst sizes from population dynamics. Using this framework, and additional literature data, we identify allometric scaling principles that constrain estimates of viral-life history traits. We discuss some of the challenges in scaling up from bottles to ecosystems, including model-measurement mismatch, how environmental drivers may affect trait plasticity, and how we might expect different viral-host systems to impact biogeochemical cycling differently.
06:00 PM
Variation in Surface Properties of Individual Bacterial Cells that Influences Viral Attachment (9096)
Primary Presenter: Yosuke Yamada, JAMSTEC / Tohoku university (yamadayo@jamstec.go.jp)
Viruses influence microbial communities and biogeochemical cycles in marine environments. Viral attachment to non-host bacterial surfaces may affect host-virus infection rates, but mechanisms remain unclear. Previous work (Yamada et al., 2023) showed that rougher bacterial surfaces enhance viral attachment. However, the variation in surface roughness among individual bacterial cells is still poorly understood, limiting insights into viral attachment mechanisms. This study used atomic force microscopy to measure the surface roughness of relatively large bacteria (spherical equivalent diameter ≥ 0.3 μm) collected along the coast of Okinawa, Japan. Surface roughness was measured in five 150 nm × 150 nm areas per cell. Results showed that some cells had uniform roughness (with up to 1.1-fold differences between areas), while others showed greater variability (up to 5.3-fold differences). This may reflect localized structures like flagella or extracellular polymers, suggesting that areas with varying viral attachment potential exist on individual cells. Finer-scale measurements (40 nm × 40 nm) also revealed that bacterial surface properties (height, Young's modulus, and adhesiveness) varied on individual cells. These nanoscale variations may impact viral attachment and infection in seawater, with potential ecological and biogeochemical implications.
06:00 PM
DIFFERENTIAL VIRAL EFFECTS ON THE GROWTH EFFICIENCY OF FRESHWATER BACTERIOPLANKTON IN EUTROPHIC VS. NON-EUTROPHIC LAKES (9815)
Primary Presenter: Telesphore Sime-Ngando, CNRS, Centre National de la Recherche Scientifique (telesphore.sime-ngando@uca.fr)
In aquatic environments, the understanding of viral influence on bacterial carbon metabolism, particularly with nutrient availability as a key factor, remains limited. To address this, we investigated viral regulation of carbon-based bacterial growth efficiency (BGE) in a series of freshwater systems in the French Massif Central, categorized into two trophic states: eutrophic and non-eutrophic lakes. Our comparative analysis revealed that microbial abundances, including both viruses and bacteria, were approximately three times higher in eutrophic lakes than in non-eutrophic ones. This pattern was mirrored by higher bacterial production and viral lytic activity in eutrophic lakes. Variability in BGE, ranging from 10% to 60%, was attributed to the decoupling of bacterial respiration from production. In eutrophic lakes, viruses had an antagonistic effect on BGE through the selective lysis of susceptible bacterial communities. In contrast, in non-eutrophic lakes, viral-induced substrate release (viral shunt) had a synergistic effect on carbon metabolism, benefiting non-target bacterial populations. The significance of these viral processes—lysis and substrate release—on BGE was further supported by the strong correlation between bacterial abundance and production, which is often considered a proxy for top-down control. Overall, the dual role of viruses, exerting negative effects through host mortality and positive effects via substrate supply, can have important implications for carbon cycling within freshwater bacterioplankton communities.
SS17P- Viral interactions and ecological dynamics
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A