title: Metaproteomics of aquatic microbial communities in a deep and stratified estuary.
abstract: Here we harnessed the power of metaproteomics to assess the metabolic diversity and function of stratified aquatic microbial communities in the deep and expansive Lower St. Lawrence Estuary, located in eastern Canada. Vertical profiling of the microbial communities through the stratified water column revealed differences in metabolic lifestyles and in carbon and nitrogen processing pathways. In productive surface waters, we identified heterotrophic populations involved in the processing of high and low molecular weight organic matter from both terrestrial (e.g. cellulose and xylose) and marine (e.g. organic compatible osmolytes) sources. In the less productive deep waters, chemosynthetic production coupled to nitrification by MG-I Thaumarchaeota and Nitrospina appeared to be a dominant metabolic strategy. Similar to other studies of the coastal ocean, we identified methanol oxidation proteins originating from the common OM43 marine clade. However, we also identified a novel lineage of methanol-oxidizers specifically in the particle-rich bottom (i.e. nepheloid) layer. Membrane transport proteins assigned to the uncultivated MG-II Euryarchaeota were also specifically detected in the nepheloid layer. In total, these results revealed strong vertical structure of microbial taxa and metabolic activities, as well as the presence of specific "nepheloid" taxa that may contribute significantly to coastal ocean nutrient cycling.
authors.affiliation: Department of Biology, Concordia University, Montreal, Quebec, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Colatriano
authors.affiliation: Department of Biology, Concordia University, Montreal, Quebec, Canada.
authors.forename: Arthi
authors.initials: A
authors.lastname: Ramachandran
authors.affiliation: National Research Council Canada, Energy, Mining and Environment, Montreal, Quebec, Canada.
authors.forename: Etienne
authors.initials: E
authors.lastname: Yergeau
authors.affiliation: Département des Sciences Biologiques, Université de Montréal, Montréal, Quebec, Canada.|Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montreal, Quebec, Canada.
authors.forename: Roxane
authors.initials: R
authors.lastname: Maranger
authors.affiliation: Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada.|Geochemistry and Geodynamics Research Center (GEOTOP), Montreal, Quebec, Canada.
authors.forename: Yves
authors.initials: Y
authors.lastname: Gélinas
authors.affiliation: Department of Biology, Concordia University, Montreal, Quebec, Canada.|Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montreal, Quebec, Canada.|Canadian Institute for Advanced Research, Integrated Microbial Biodiversity Program, Toronto ON, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Walsh
mesh_terms: D001105:Archaea / Q000235:genetics*; D001419:Bacteria / Q000235:genetics*; D002170:Canada; D002244:Carbon / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D056186:Metagenomics; D058465:Nitrification / Q000235:genetics; D009584:Nitrogen / Q000378:metabolism; D040901:Proteomics; D014871:Water Microbiology
chemical_list: D026901:Membrane Transport Proteins; D002244:Carbon; D009584:Nitrogen
keywords: Carbon cycle; Marine microbiology; Metagenomics; Microbiology; Nitrification; Ocean