Personne : Lovejoy, Connie
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Lovejoy
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Connie
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Université Laval. Département de biologie
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ncf11850007
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Publication Accès libre Chlorovirus and myovirus diversity in permafrost thaw ponds(Inter-Research Science Publisher, 2018-12-17) Culley, Alexander; Lovejoy, Connie; Comte, Jérôme; Vincent, Warwick F.; Lévesque, AlicePermafrost thaw ponds occur in high abundance across the northern landscape of Canada and are sites of intense microbial activity, resulting in carbon dioxide and methane emissions to the atmosphere. In this study, we focused on viruses as largely unstudied agents of top-down control in these high-latitude microbial ecosystems. Specifically, we compared the diversity of myovirus, chlorovirus and host microbial communities in an organic soil palsa valley pond and a mineral soil lithalsa valley pond. These 2 subarctic permafrost landscapes are both common in northern Québec, Canada. Sequence analysis of ribosomal small subunit RNA genes showed that the community structure of bacteria and microbial eukaryotes differed significantly between the 2 ponds, which both differed from microbial communities in a rock-basin lake (whose formation was not related to permafrost thawing and which we used as a reference pond) in the same region. The viral assemblages included 439 OTUs in the uncultured Myoviridae category and 41 OTUs in the family Phycodnaviridae. Phylogenetic analysis of the latter based on an amino acid sequence alignment revealed a single large clade related to chloroviruses, consistent with the abundant presence of chlorophytes in these waters. As there was for the bacterial and eukaryotic communities, there were also significant differences in the community structure of these viral groups among the 3 ponds. These results suggest that host community composition is influenced by environmental filtering, which in turn contributes to driving viral diversity across landscape types.Publication Accès libre Genomic evidence for sulfur intermediates as new biogeochemical hubs in a model aquatic microbial ecosystem(2021-02-16) Culley, Alexander; Lovejoy, Connie; Vincent, Warwick F.; Vigneron, Adrien; Couture, Raoul-Marie; Cruaud, PerrineBackground The sulfur cycle encompasses a series of complex aerobic and anaerobic transformations of S-containing molecules and plays a fundamental role in cellular and ecosystem-level processes, influencing biological carbon transfers and other biogeochemical cycles. Despite their importance, the microbial communities and metabolic pathways involved in these transformations remain poorly understood, especially for inorganic sulfur compounds of intermediate oxidation states (thiosulfate, tetrathionate, sulfite, polysulfides). Isolated and highly stratified, the extreme geochemical and environmental features of meromictic ice-capped Lake A, in the Canadian High Arctic, provided an ideal model ecosystem to resolve the distribution and metabolism of aquatic sulfur cycling microorganisms along redox and salinity gradients. Results Applying complementary molecular approaches, we identified sharply contrasting microbial communities and metabolic potentials among the markedly distinct water layers of Lake A, with similarities to diverse fresh, brackish and saline water microbiomes. Sulfur cycling genes were abundant at all depths and covaried with bacterial abundance. Genes for oxidative processes occurred in samples from the oxic freshwater layers, reductive reactions in the anoxic and sulfidic bottom waters and genes for both transformations at the chemocline. Up to 154 different genomic bins with potential for sulfur transformation were recovered, revealing a panoply of taxonomically diverse microorganisms with complex metabolic pathways for biogeochemical sulfur reactions. Genes for the utilization of sulfur cycle intermediates were widespread throughout the water column, co-occurring with sulfate reduction or sulfide oxidation pathways. The genomic bin composition suggested that in addition to chemical oxidation, these intermediate sulfur compounds were likely produced by the predominant sulfur chemo- and photo-oxidisers at the chemocline and by diverse microbial degraders of organic sulfur molecules. Conclusions The Lake A microbial ecosystem provided an ideal opportunity to identify new features of the biogeochemical sulfur cycle. Our detailed metagenomic analyses across the broad physico-chemical gradients of this permanently stratified lake extend the known diversity of microorganisms involved in sulfur transformations over a wide range of environmental conditions. The results indicate that sulfur cycle intermediates and organic sulfur molecules are major sources of electron donors and acceptors for aquatic and sedimentary microbial communities in association with the classical sulfur cycle.