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Ramachandran A.,Concordia University at Montreal | Walsh D.A.,Concordia University at Montreal | Walsh D.A.,Canadian Institute for Advanced Research | Walsh D.A.,Groupe Of Recherche Interuniversitaire En Limnologie Gril
FEMS Microbiology Ecology | Year: 2015

The diversity and distribution of methylotrophic bacteria have been investigated in the oceans and lakes using the methanol dehydrogenase mxaF gene as a functional marker. However, pelagic marine (OM43) and freshwater (LD28 and PRD01a001B) methylotrophs within the Betaproteobacteria lack mxaF, instead possessing a related xoxF4-encoded methanol dehydrogenase. Here, we developed and employed xoxF4 as a complementary functional gene marker to mxaF for studying methylotrophs in aquatic environment. Using xoxF4, we detected OM43-related and LD28-related methylotrophs in the ocean and freshwaters of North America, respectively, and showed the coexistence of these two lineages in a large estuarine system (St Lawrence Estuary). Gene expression patterns of xoxF4 supported a positive relationship between xoxF4-containing methylotroph activity and spring time productivity, suggesting phytoplankton blooms are a source of methylotrophic substrates. Further investigation of methanol dehydrogenase diversity in pelagic ecosystems using comparative metagenomics provided strong support for a widespread distribution of xoxF4 (as well as several distinct xoxF5) containing methylotrophs in marine and freshwater surface waters. In total, these results demonstrate a geographical distribution of OM43/LD28-related methylotrophs that includes marine and freshwaters and suggest that methylotrophy occurring in the water column is an important component of lake and estuary carbon cycling and biogeochemistry. © FEMS 2015. Source

Colatriano D.,Concordia University at Montreal | Ramachandran A.,Concordia University at Montreal | Yergeau E.,National Research Council Canada | Maranger R.,University of Montreal | And 6 more authors.
Proteomics | Year: 2015

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Beaulieu M.,McGill University | Beaulieu M.,Groupe Of Recherche Interuniversitaire En Limnologie Gril | Pick F.,University of Ottawa | Gregory-Eaves I.,McGill University | Gregory-Eaves I.,Groupe Of Recherche Interuniversitaire En Limnologie Gril
Limnology and Oceanography | Year: 2013

Using a ~ 1000 lake data set that spans the entire continental United States, we applied empirical modeling approaches to quantify the relative strength of nutrients and water temperature as predictors of cyanobacterial biomass (CBB). Given that cyanobacteria possess numerous traits providing competitive advantage under warmer conditions, we hypothesized that water temperature, in addition to nutrients, is a significant predictor of CBB. Total nitrogen (TN), water temperature, and total phosphorus were all significant predictors of CBB, with TN explaining the most variance. Using multiple linear regression analysis, we found that TN and water temperature provided the best model and explained 25% of the variance in CBB. However, when the data set was divided according to basin type, these same variables explained a higher amount of the variation in deep natural lakes (33%, n = 253), whereas the least amount of variation was explained by these variables in shallow reservoirs (12%, n = 307). Competing path models on the full data set using the best variables selected by multiple linear regression show that nitrogen and temperature are indirectly linked to cyanobacteria by association with total algal biomass, which likely reflects changes in light climate and other secondary factors. Our models also indicated that temperature was linked to cyanobacteria by a direct pathway. Under a scenario of atmospheric CO2 doubling from 1990 levels (resulting in an estimated 3.3°C increase of the maximum lake surface water), we predict on average a doubling of CBB. © 2013, by the Association for the Sciences of Limnology and Oceanography, Inc. Source

Le Jeune A.-H.,Groupe Of Recherche Interuniversitaire En Limnologie Gril | Le Jeune A.-H.,CNRS Microorganisms Laboratory: Genome and Environment | Bourdiol F.,Groupe Of Recherche Interuniversitaire En Limnologie Gril | Bourdiol F.,National Polytechnic Institute of Toulouse | And 4 more authors.
Environmental Pollution | Year: 2012

MeHg biomagnification by the phantom midge Chaoborus in relation to MeHg concentrations in their prey and its migratory behavior was investigated in two Canadian Precambrian Shield lakes. Three Chaoborus species with contrasted migratory behavior were collected in a fishless and a fish-inhabited lake. All species accumulated MeHg through their ontogenic development. In the lake inhabited by fish, all instars of Chaoborus punctipennis displayed a marked migratory behavior and were unable to biomagnify MeHg, whereas in the fishless lake, Chaoborus americanus and Chaoborus trivittatus biomagnified MeHg. Reduced biomagnification capacity of C. trivittatus, the coexisting species living with C. americanus, was also ascribed to a progressive vertical segregation with age. Growth dilution, amount and type of prey items or trophic position could not explain the different patterns of biomagnification. Our findings demonstrate that the most common invertebrate predator of temperate planktonic food webs can biomagnify mercury, contrarily to previous reports. © 2012 Elsevier Ltd. All rights reserved. Source

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