Distinct viral influences on particle-associated vs. free-living bacterial communities and particulate vs. dissolved elemental pools

Viruses tightly regulate microbial community metabolism and activities, but does viral control differ for particle-associated (PA) vs free-living (FL) bacteria and the partitioning of elements between the particulate and dissolved pools? Resolving viral influences across size fractions is relevant in aquatic systems as PA vs FL bacteria play varying roles in carbon remineralization and may have distinct susceptibility to viruses. We performed a virus enrichment experiment and coupled metagenomics, metabolomic, geochemical analyses and enzyme assays to study viral control of freshwater PA and FL bacteria and biogeochemical cycles in an oligotrophic lake and a peat bog lake. We found the environmental dependence of virus-host dynamics: a nearly 10-fold enrichment in virus:bacteria ratio increased cell lysis but only in the peat bog lake. We also found that: 1) viral regulation was strongest for PA bacteria; 2) viral infection of PA bacteria promoted enzyme production to scavenge for carbon and phosphorus; 3) increased lysis, which releases sticky exopolymeric substances, likely promoted the flocculation of high O:C, but low H:C dissolved compounds into particulate organic matter; 4) over 100 dissolved organic matter (DOM) ‘peaks’ from the metabolomic data were only detectable with increased lysis, indicating a viral impact on the DOM pool; and 5) viral auxiliary metabolic genes related to carbon and phosphorus cycling were abundant in metagenomes. These findings highlight distinct viral influences on PA vs FL bacterial communities and biogeochemical cycling.

Presentation Preference: Either

Primary Presenter: John Paul Balmonte, Lehigh University (jp.balmonte@gmail.com)

Authors:

John Paul Balmonte, Lehigh University  (jpb422@lehigh.edu)

Maliheh Mehrshad, Swedish University of Agricultural Sciences  (maliheh.mehrshad@slu.se)

Anders Torstensson, Swedish Meteorological and Hydrological Institute  (anders.torstensson@smhi.se)

Jeffrey Hawkes, Uppsala University  (jeffrey.hawkes@kemi.uu.se)

Anna Szekely, Swedish University of Agricultural Sciences  (anna.szekely@slu.se)