Cassandre Sara Lazar

Cassandre Sara Lazar
Université du Québec à Montréal | UQAM · Department of Biological Sciences

PhD

About

32
Publications
9,480
Reads
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1,349
Citations
Citations since 2016
19 Research Items
1235 Citations
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
Additional affiliations
August 2017 - present
Université du Québec à Montréal
Position
  • Professor
April 2014 - June 2017
Friedrich Schiller University Jena
Position
  • PostDoc Position
September 2010 - March 2014
University of North Carolina at Chapel Hill
Position
  • PostDoc Position

Publications

Publications (32)
Article
Aquifers are inhabited by microorganisms from the three major domains of life: archaea, eukaryotes and bacteria. Although interest in the processes that govern the assembly of these microbial communities is growing, their study is almost systematically limited to one of the three domains of life. Archaea, bacteria and eukaryotes are however interco...
Article
Full-text available
In freshwater ecosystems, dynamic hydraulic events (floods or dam maintenance) lead to sediment resuspension and mixing with waters of different composition. Microbial communities living in the sediments play a major role in these leaching events, contributing to organic matter degradation and the release of trace elements. However, the dynamics of...
Article
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Each year, millions of tons of sodium chloride are dumped on roads, contributing to the salinization of freshwater environments. Thus, we sought to understand the effect of sodium chloride (NaCl) on freshwater lake prokaryotic communities, an important and understudied component of food webs. Using mesocosms with 0.01–2.74 ppt NaCl (0.27–1110.86 mg...
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Full-text available
Microbial communities play an important role in shallow terrestrial subsurface ecosystems. Most studies of this habitat have focused on planktonic communities that are found in the groundwater of aquifer systems and only target specific microbial groups. Therefore, a systematic understanding of the processes that govern the assembly of endolithic a...
Article
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Freshwater salinization is a widespread issue, but evidence of ecological effects on aquatic communities remains scarce. We experimentally exposed salt‐naive plankton communities of a north‐temperate, freshwater lake to a gradient of chloride (Cl−) concentration (0.27–1400 mg Cl L−1) with in situ mesocosms. Following 6 weeks, we measured changes in...
Chapter
Cold seeps host intense and complex biochemical processes, in particular methane and sulfur cycling. Microorganisms are key players in these habitats, producing or oxidizing methane, and reducing sulfate. Mediterranean cold seep mud volcanoes are natural laboratories allowing to study how reducing fluids from different volcanoes with distinct conne...
Article
Terrestrial subsurface microbial communities are not restricted to the fluid-filled void system commonly targeted during groundwater sampling but are able to inhabit and dwell in rocks. However, compared to the exploration of the deep biosphere, endolithic niches in shallow sedimentary bedrock have received little interest so far. Despite the poten...
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Full-text available
Marine sediments host an unexpectedly large microbial biosphere, suggesting unique microbial mechanisms for surviving burial and slow metabolic turnover. Although dormancy is generally considered an important survival strategy, its specific role in subsurface sediments remains unclear. We quantified dormant bacterial endospores in 331 marine sedime...
Article
Microbial production of methane is an important terminal metabolic process during organic matter degradation in marine sediments. It is generally acknowledged that hydrogenotrophic and acetoclastic methanogenesis constitute the dominant pathways of methane production; the importance of methanogenesis from methylated compounds remains poorly underst...
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Isotopes of dissolved inorganic carbon (DIC) are used to indicate both transit times and biogeochemical evolution of groundwaters. These signals can be complicated in carbonate aquifers, as both abiotic (i.e., carbonate equilibria) and biotic factors influence the δ¹³C and ¹⁴C of DIC. We applied a novel graphical method for tracking changes in the...
Article
Full-text available
Groundwater environments provide habitats for diverse microbial communities, and although Archaea usually represent a minor fraction of communities, they are involved in key biogeochemical cycles. We analysed the archaeal diversity within a mixed carbonate-rock/siliciclastic-rock aquifer system, vertically from surface soils to subsurface groundwat...
Article
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Along a long-term ecosystem development gradient, soil nutrient contents and mineralogical properties change, therefore probably altering soil microbial communities. However, knowledge about the dynamics of soil microbial communities during long-term ecosystem development including progressive and retrogressive stages is limited, especially in mine...
Article
Full-text available
The ISME Journal: Multidisciplinary Journal of Microbial Ecology is the official Journal of the International Society for Microbial Ecology, publishing high-quality, original research papers, short communications, commentary articles and reviews in the rapidly expanding and diverse discipline of microbial ecology.
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Full-text available
Savannas cover at least 13% of the global terrestrial surface and are often nutrient limited, especially by nitrogen. To gain a better understanding of their microbial diversity and the microbial nitrogen cycling in savanna soils, soil samples were collected along a granitic and a basaltic catena in Kruger National Park (South Africa) to characteri...
Article
Nature Microbiology 1 , 16002 (2016); published 15 February 2016; corrected 6 June 2016. This Letter should have been published under a Creative Commons licence according to the Nature policy on publishing the primary sequence of an organism's genome for the first time.
Article
Importance: This study provides multiple lines of evidence to show that microbes are the main drivers of Mn(II) oxidation even at acidic pH, offering new insights into Mn biogeochemical cycling. A distinct, highly adapted microbial community inhabits acidic, oligotrophic Mn deposits and mediates biological Mn oxidation. These data highlight the im...
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Full-text available
The subsurface biosphere is largely unexplored and contains a broad diversity of uncultured microbes1. Despite being one of the few prokaryotic lineages that is cosmopolitan in both the terrestrial and marine subsurface2, 3, 4, the physiological and ecological roles of SAGMEG (South-African Gold Mine Miscellaneous Euryarchaeal Group) Archaea are un...
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Marine and estuary sediments contain a variety of uncultured archaea whose metabolic and ecological roles are unknown. De novo assembly and binning of high-throughput metagenomic sequences from the sulfate-methane transition zone in estuary sediments resulted in the reconstruction of three partial to near-complete (2.4-3.9 Mb) genomes belonging to...
Article
Investigations of the biogeochemical roles of benthic Archaea in marine sediments are hampered by the scarcity of cultured representatives. In order to determine their metabolic capacity, we reconstructed the genomic content of four widespread uncultured benthic archaea recovered from estuary sediments at 48 to 95% completeness. Four genomic bins w...
Article
We investigated the microbial community compositions in two sediment samples from the acidic (pH ∼3) and hypersaline (> 4.5% NaCl) surface waters which are widespread in Western Australia. In West Dalyup River, large amounts of NaCl, Fe(II) and sulfate are brought by the groundwater into the surface runoff. The presence of K-jarosite and schwertman...
Article
Studies on microbial carbon cycling uniformly confirm that anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria represent the dominant and most active fraction of the sedimentary microbial community in methane-seep sediments. However, little is known about other frequently observed and abundant microbial taxa, their role in carb...
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Full-text available
Estuaries are among the most productive habitats on the planet. Bacteria in estuary sediments control the turnover of organic carbon and the cycling of nitrogen and sulfur. These communities are complex and primarily made up of uncultured lineages, thus little is known about how ecological and metabolic processes are partitioned in sediments. De no...
Article
The anoxic sediments of the White Oak River (WOR) estuary comprise a distinctive sulfate-methane transition zone (SMTZ) and natural enrichment of the archaea affiliated with the Miscellaneous Crenarchaeota Group (MCG). Archaeal biphytanes were generally depleted in 13C, with δ13C values being less than -35‰, indicative of production by active sedim...
Article
Sediments of the White Oak River estuary situated on the coast of North Carolina harbor one of the most diverse known populations of uncultured Archaea, specifically the Miscellaneous Crenarchaeotal Group (MCG). In order to constrain the environmental factors influencing the uncultured archaeal groups in the WOR estuary, biogeochemical profiles as...
Article
Ethane and propane are low molecular weight hydrocarbons observed widely at trace levels in cold marine sediments where thermogenic sources are considered insignificant, but their biological sources remain poorly constrained. In this study, several C-2 and C-3 compounds including alkenes, alcohols, thiols and carboxylic acids with a C-2 or C-3 skel...
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Recently, small Idas-like mussels have been discovered living on carbonate crusts associated with cold-seeps in the Marmara Sea. These mussels, here referred to as Idas-like nov. sp., differ morphologically and genetically from another species identified as Idas aff. modiolaeformis, living in the same type of ecosystem in the Nile Deep-Sea Fan (eas...
Article
Marine mud volcanoes are geological structures emitting large amounts of methane from their active centres. The Amsterdam mud volcano (AMV), located in the Anaximander Mountains south of Turkey, is characterized by intense active methane seepage produced in part by methanogens. To date, information about the diversity or the metabolic pathways used...
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Full-text available
Pockmarks are seabed geological structures sustaining methane seepage in cold seeps. Based on RNA-derived sequences the active fraction of the archaeal community was analysed in sediments associated with the G11 pockmark, in the Nyegga region of the Norwegian Sea. The anaerobic methanotrophic Archaea (ANME) and sulfate-reducing bacteria (SRB) commu...
Article
Submarine mud volcanoes are a significant source of methane to the atmosphere. The Napoli mud volcano, situated in the brine-impacted Olimpi Area of the Eastern Mediterranean Sea, emits mainly biogenic methane particularly at the centre of the mud volcano. Temperature gradients support the suggestion that Napoli is a cold mud volcano with moderate...
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Full-text available
Microbial mats in marine cold seeps are known to be associated with ascending sulfide- and methane-rich fluids. Hence, they could be visible indicators of anaerobic oxidation of methane (AOM) and methane cycling processes in underlying sediments. The Napoli mud volcano is situated in the Olimpi Area that lies on saline deposits; from there, brine f...
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Full-text available
Siboglinid tubeworms in cold seep sediments can locally modify the geochemical gradients of electron acceptors and donors, hence creating potential microhabitats for prokaryotic populations. The archaeal communities associated with sediments populated by Oligobrachia haakonmosbiensis and Sclerolinum contortum Siboglinid tubeworms in the Storegga Sl...

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Projects

Projects (3)
Project
Development of new tools for georesources exploration and development such as Predikor, BEARD, UnBOX using AI techniques (developed by Geolearn) or MicroGeoNx using microorganism DNA sequencing for lithostratigraphy studies (developed by Lazar & Marcil a UQAM-DerenaGeosciences partnership).
Project
Understanding the Links Between Surface and Subsurface Biogeosphere The Collaborative Research Center AquaDiva focusses on the important roles of water (Aqua) and biodiversity (Diva) for shaping the structure, properties and functions of the subsurface , defined here as the zone that begins below the highest density of plant roots (~0.3 meters) down into the first aquifers (~100 meters). Our project seeks to answer fundamental questions about this part of the Earth’s Critical Zone (CZ): What biota live there? How do they interact with and reflect their environment? How do they reflect surface properties? The CZ is increasingly impacted by humans, yet we have little understanding of the consequences for ecosystem services such as groundwater quality and supply, stabilization of carbon, and trace gas cycling on which people in turn rely. The overall research question of the CRC AquaDiva "How do surface conditions and local geology set the functional biodiversity of the subsurface?" requires us to explore how these factors interact to shape the subsurface environment and its impacts. To answer this question we established a Critical Zone Exploratory (CZE) which builds on a three-factor experimental design, i.e., land use (factor 1), CZ subsurface compartment (factor 2), and alkaline versus acidic geologic setting (factor 3). Within this approach, we apply a combination of complementary field and laboratory investigations at different spatial scales to determine how surface conditions and geologic constraints impact subsurface biodiversity and function. We concentrate on investigating how processes of fluid flow, matter and energy transport link surface processes (atmosphere, climate, vegetation, and topsoil horizons) to subsurface biodiversity and function along gradients of land management and surface biodiversity within a transect underlain by limestone and siliciclastic rocks. Our efforts build on an infrastructure of existing wide bore groundwater wells, the characterization of surface properties in the Biodiversity Exploratory Hainich-Dün, and a grassland biodiversity experiment (The Jena Experiment). The AquaDiva-research team is organized into three scientific teams: BIODIV investigators will identify and trace biomarkers of specific organisms, functions or processes and further use molecular-based methods to study subsurface functional biodiversity. FLUX investigators will use a range of tracer methods, field monitoring, and models to determine the rates of vertical and lateral transport of water, energy, genetic material, mobile organic matter, colloids, particles, elements, and gases. GEOFACTS investigators will focus on the geological and physical structures of the subsurface as well as the chemical interactions with the biota, such as mineral formation and weathering. The research teams are supprted by the INFRA projects that manage and coordinate common sampling and analysis, data sharing, analysis and archiving, and a doctoral program for students in the project.