title: Viral and grazer regulation of prokaryotic growth efficiency in temperate freshwater pelagic environments.
abstract: In aquatic systems, limited data exists on the impact of mortality forces such as viral lysis and flagellate grazing when seeking to explain factors regulating prokaryotic metabolism. We explored the relative influence of top-down factors (viral lysis and heterotrophic nanoflagellate grazing) on prokaryotic mortality and their subsequent impact on their community metabolism in the euphotic zone of 21 temperate freshwater lakes located in the French Massif Central. Prokaryotic growth efficiency (PGE, index of prokaryotic community metabolism) determined from prokaryotic production and respiration measurements varied from 5 to 74% across the lakes. Viral and potential grazer-induced mortality of prokaryotes had contrasting impact on PGE. Potential flagellate grazing was found to enhance PGE whereas viral lysis had antagonistic impacts on PGE. The average PGE value in the grazing and viral lysis dominated lake water samples was 35.4% (±15.2%) and 17.2% (±8.1%), respectively. Selective viral lysis or flagellate grazing on prokaryotes together with the nature of contrasted substrates released through mortality processes can perhaps explain for the observed variation and differences in PGE among the studied lakes. The influences of such specific top-down processes on PGE can have strong implications on the carbon and nutrient fluxes in freshwater pelagic environments.
authors.affiliation: Laboratoire Microorganismes : Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, BP 80026, 63171 Aubière Cedex, France Pradeep_Ram.ANGIA_SRIRAM@univ_bpclermont.fr.
authors.forename: A S
authors.initials: AS
authors.lastname: Pradeep Ram
authors.affiliation: Laboratoire Microorganismes : Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, BP 80026, 63171 Aubière Cedex, France.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Colombet
authors.affiliation: Laboratoire Microorganismes : Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, BP 80026, 63171 Aubière Cedex, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Perriere
authors.affiliation: Athos Environnement, Université Blaise Pascal, BP 80026, 63171 Aubière Cedex, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Thouvenot
authors.affiliation: Laboratoire Microorganismes : Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, BP 80026, 63171 Aubière Cedex, France.
authors.forename: Telesphore
authors.initials: T
authors.lastname: Sime-Ngando
mesh_terms: D002244:Carbon / Q000378:metabolism; D017753:Ecosystem; D052836:Heterotrophic Processes / Q000502:physiology*; D060106:Lakes / Q000382:microbiology* / Q000821:virology*; D064307:Microbiota / Q000502:physiology*; D011387:Prokaryotic Cells / Q000378:metabolism*; D014871:Water Microbiology
chemical_list: D002244:Carbon
keywords: heterotrophic nanoflagellate grazing potential; lakes of French Massif Central; prokaryotes; prokaryotic growth efficiency; viral lysis; viruses