Mixing alters the lytic activity of viruses in the dark ocean

Abstract

In aquatic habitats, viral lysis of prokaryotic cells lowers the overall efficiency of the microbial loop, by which dissolved organic carbon is transfered to higher trophic levels. Mixing of water masses in the dark ocean occurs on a global scale and may have far reaching consequences for the different prokaryotic and virus communities found in these waters by altering the environmental conditions these communities experience. We hypothesize that mixing of deep ocean water masses enhances the lytic activity of viruses infecting prokaryotes. To address this hypothesis, major deep‐sea water masses of the Atlantic Ocean such as North Atlantic Deep Water, Mediterranean Sea Overflow Water, Antarctic Intermediate Water, and Antarctic Bottom Water were sampled at five locations. Prokaryotic cells from these samples were collected by filtration and subsequently incubated in virus‐reduced water from either the same (control) or a different water mass (transplantation treatment). Additionally, mixtures of prokaryotes obtained from two different water masses were incubated in a mixture of virus‐reduced water from the same water masses (control) or in virus‐reduced water from the source water masses separately (mixing treatments). Pronounced differences in productivity‐related parameters (prokaryotic leucine incorporation, prokaryotic and viral abundance) between water masses caused strong changes in viral lysis of prokaryotes. Often, mixing of water masses increased viral lysis of prokaryotes, indicating that lysogenic viruses were induced into the lytic cycle. Mixing‐induced changes in viral lysis had a strong effect on the community composition of prokaryotes and viruses. Our data show that mixing of deep‐sea water masses alters levels of viral lysis of prokaryotes and in many cases weakens the efficiency of the microbial loop by enhancing the recycling of organic carbon in the deep ocean.

Genome‐resolved viral and cellular metagenomes revealed potential key virus‐host interactions in a deep freshwater lake

“…The second shift in the virion community from December to January likely resulted from the onset of winter vertical mixing (Supporting Information Table S1), which intermingled the epilimnetic and hypolimnetic viral communities, as observed for bacterioplankton (Okazaki et al ., , ; Okazaki and Nakano, ). Alternatively, environmental stresses associated with the mixing event (e.g., increased solar radiation) could have induced lysogens in the lytic cycle (Winter et al ., ) and resulted in the observed viral community shift.…”

Viral control of biomass and diversity of bacterioplankton in the deep sea

“…22 ). For the deep-sea, such environmental changes could include the mixing of water masses 23 , sinking particles, or the in situ formation of particles (e.g., see ref. 14 ).…”

Picoplankton Distribution and Activity in the Deep Waters of the Southern Adriatic Sea

“…Water mass sinking to the SAP could cause the induction of lysogenic viruses and thus keep the viral abundance stable. Winter et al [102] recently pointed out that mixing in the deeper waters led to the induction of lysogenic viruses. Viruses positively correlated with the members of the picoplankton community at the sampling sites, indicating their involvement in shaping the picoplankton abundances in the oligotrophic waters of the SAP.…”