Viral Attachment to Biotic and Abiotic Surfaces in Seawater

Viruses influence microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces could influence host viral infection rates; however, the prevalence of such viral attachment is not investigated quantitatively. We used coastal seawater viral assemblages and, as models, marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) to investigate their attachment to probable nonhost marine bacteria. We also studied viral attachment to colloids and other abiotic surfaces in seawater. Centrifugation experiments with bacterium-virus mixtures showed substantial viral loss in the supernatant presumably due to the viral attachment to bacteria. This attachment (0.04 to 24 viruses μm^-2 [bacterial surface area]) varied with bacterium-virus combinations. Surprisingly, filtering seawater on 0.2-μm Anodisc or polycarbonate filters retained ∼12 to 84% of viruses presumably attached to ≥0.2-μm-sized particles and/or the filter surface. Enzymatic digestion followed by epifluorescence and atomic force microscopy suggested that 7 to 25% of the total viruses were attached via β-glycosidic linkages. Furthermore, a substantial proportion (7 to 48%) of viruses became attached to model abiotic surfaces (polycarbonate, polypropylene, and glass), and this has significance for laboratory protocols as well as studies of virus ecology in particle-rich marine environments. Substantial attachment of viruses to nonhost surfaces could influence virus-driven biogeochemical cycles and microbial community structure.IMPORTANCE Viruses play important roles in altering microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces can influence host viral infection rates; however, the prevalence of viral attachment to nonhost surfaces and the ratio of attached viruses to total viruses are little known. We used coastal seawater viral assemblages and used marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) as models to investigate their attachment to abiotic and biotic surfaces in seawater. Viral attachment was observed on several surfaces, such as nonhost bacteria, polymers, filters, cover glasses, and tube surfaces. This study cautions against commonly used protocols that require viral incubation and seawater fractionation. More importantly, these results could influence virus-driven biogeochemical cycles and microbial community structure in the ocean.