Roles of viral infection in organic particle flux

Abstract

Lack of information on the fate of particulate-associated microorganisms prompted this investigation of viruses (including bacteriophage or phage) and phage-infected cells in sinking particles from sediment traps. Sediment trap material from 30 to 400 m collected from the north Pacific Ocean during the 'VERTEX' cruises in 1980 to 1982 was examined by transmission electron microscopy. Viruses were present in all of the sinking particles examined except for those from one sample, of highly degraded algal cells or small fecal pellets, from 400 m. Viruses in the sinking particles often appeared aggregated. From 0.7 to 3.7 O/O of the bacteria in sinking particles contained mature phage; from these data and limited information from pure cultures, we estimate that 2 to 37 % of the particulate-associated bacteria may be killed by viral lysis. Many eukaryotic cells were also apparently infected with viruses, but none ( 5 50 cells observed) of the cyanobacteria or 'Chlorella-like' cells appeared infected. Viral lysis of bacteria associated with sinking particles and free-living bacteria may be causally linked and may play a role in dissolved organic carbon production and the dynamics of sinking particles. Viral lysis may have major implications for understanding cycling of material and energy in the ocean.