Biology subjects

Moreau, J. W.

Publications and source records attributed to Moreau, J. W..

5 recordsLinked to original sources

bioRxiv2020

Evaluating the impacts of microbial activity and species interactions on passive bioremediation of a coastal acid sulfate soil (CASS) ecosystem

Microbial iron and sulfate reduction are the primary drivers of coastal acid sulfate soil (CASS) passive bioremediation schemes. Microbial sulfate reduction is the limiting step for pyrite formation, a desirable endpoint for CASS remediation. Little is known, however, about the impacts of microbial activity or species interaction on long-term iron and sulfur cycling in CASS ecosystems. Using a combination of molecular biology, geochemical speciation and artificial intelligence-powered computational modeling, we deduced from microbial activity patterns (RNA-based) and geochemical measurements a best-fit equation for predicting biogeochemical pyrite formation in a model CASS ecosystem. In addition to the time-dependent activities of key sulfate-reducing prokaryotic taxa (e.g. Desulfobacteraceae), this equation required methylotrophs (Methylobacteriaceae) and bacterial predators (Bacteriovorax) for best-fitting, suggesting that specific microbial interactions exert meaningful influences on CASS bioremediation efficiency. Our findings confirmed that CASS microorganisms act as an assemblage in response to rewetting by tidewater. Accurate predictions of long-term CASS bioremediation efficiency require modelling of complex and interdependent relationships between geochemical speciation and microbial activity.HighlightsCoastal acid sulfate soil (CASS) is a global environmental issue.Microbial activity can be modelled quantitatively to predict CASS remediation.Sulfate-reducing prokaryotes (SRP) play a key role in CASS remediation.Predation on SRP with cultured representatives occurred during early wet-up.The above mechanism leads to increased activity among uncultured SRP.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

Subsurface carbon monoxide oxidation capacity revealed through genome-resolved metagenomics of a carboxydotroph

Microbial communities play important roles in the biogeochemical cycling of carbon in the Earths deep subsurface. Previously, we demonstrated changes to the microbial community structure of a deep aquifer (1.4 km) receiving 150 tons of injected supercritical CO2 (scCO2) in a geosequestration experiment. The observed changes support a key role in the aquifer microbiome for the thermophilic CO-utilising anaerobe Carboxydocella, which decreased in relative abundance post-scCO2 injection. Here, we present results from more detailed metagenomic profiling of this experiment, with genome resolution of the native carboxydotrophic Carboxydocella. We demonstrate a switch in CO-oxidation potential by Carboxydocella through analysis of its carbon monoxide dehydrogenase (CODH) gene before and after the geosequestration experiment. We discuss the potential impacts of scCO2 on subsurface flow of carbon and electrons from oxidation of the metabolic intermediate carbon monoxide (CO). Originality-Significance StatementThe research conducted in this study is associated with one of the worlds largest demonstrations of carbon geosequestration - The Cooperative Research Centre for Greenhouse Gas Technologies Otway Project (Victoria, Australia). Our results expand the ecology of CO-utilising microbes to include the terrestrial deep subsurface through genome-resolved metagenomics of an aquifer-native carboxydotroph.

microbiology↗

bioRxiv2020

The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings

Bioremediation systems represent an environmentally sustainable approach to degrading industrially-generated thiocyanate (SCN-), with low energy demand and operational costs, and high efficiency and substrate specificity. However, heavy metals present in mine tailings effluent may hamper process efficiency by poisoning thiocyanate-degrading microbial consortia. Here we experimentally tested the tolerance of an autotrophic SCN--degrading bacterial consortium enriched from gold mine tailings for Zn, Cu, Ni, Cr, and As. All of the selected metals inhibited SCN- biodegradation to different extents, depending on concentration. At pH of 7.8 and 30{degrees}C, complete inhibition of SCN- biodegradation by Zn, Cu, Ni, and Cr occurred at 20, 5, 10, and 6 mg L-1, respectively. Lower concentrations of these metals decreased the rate of SCN- biodegradation, with relatively long lag times. Interestingly, the microbial consortium tolerated As even at 500 mg L-1, although both the rate and extent of SCN- biodegradation were affected. This study highlights the importance of considering metal co-contamination in bioreactor design and operation for SCN- bioremediation at mine sites. Key pointsO_LIBoth the efficiency and rate of SCN- biodegradation were inhibited by heavy metals, to different degrees depending on type and concentration of metal C_LIO_LIThe autotrophic microbial consortium was capable of tolerating high levels of As C_LI

microbiology↗

bioRxiv2020

Mercury methylation by metabolically versatile and cosmopolitan marine bacteria

Microbes transform aqueous mercury (Hg) into methylmercury (MeHg), a potent neurotoxin in terrestrial and marine food webs. This process requires the gene pair hgcAB, which encodes for proteins that actuate Hg methylation, and has been well described for anoxic environments. However, recent studies report potential MeHg formation in suboxic seawater, although the microorganisms involved remain poorly understood. In this study, we conducted large-scale multi-omic analyses to search for putative microbial Hg methylators along defined redox gradients in Saanich Inlet (SI), British Columbia, a model natural ecosystem with previously measured Hg and MeHg concentration profiles. Analysis of gene expression profiles along the redoxcline identified several putative Hg methylating microbial groups, including Calditrichaeota, SAR324 and Marinimicrobia, with the last by far the most active based on hgc transcription levels. Marinimicrobia hgc genes were identified from multiple publicly available marine metagenomes, consistent with a potential key role in marine Hg methylation. Computational homology modelling predicted that Marinimicrobia HgcAB proteins contain the highly conserved structures required for functional Hg methylation. Furthermore, a number of terminal oxidases from aerobic respiratory chains were associated with several SI putative novel Hg methylators. Our findings thus reveal potential novel marine Hg-methylating microorganisms with a greater oxygen tolerance and broader habitat range than previously recognised.

microbiology↗

bioRxiv2020

Genome-resolved metagenomics and detailed geochemical speciation analyses yield new insights into microbial mercury cycling in geothermal springs

Geothermal systems emit substantial amounts of aqueous, gaseous and methylated mercury, but little is known about microbial influences on mercury speciation. Here we report results from genome-resolved metagenomics and mercury speciation analysis of acid warm springs in the Ngawha Geothermal Field (<55 {degrees}C, pH < 4.5), Northland Region, Aotearoa (New Zealand). Our aim was to identify the microorganisms genetically equipped for mercury methylation, demethylation, or Hg(II) reduction to volatile Hg(0) in these springs. Dissolved total and methylated mercury concentrations in two adjacent springs with different mercury speciation ranked among the highest reported from natural sources (250-16000 ng L-1 and 0.5-13.9 ng L-1, respectively). Total solid mercury concentrations in spring sediments ranged from 1273 to 7000 {micro}g g-1. In the context of such ultra-high mercury levels, the geothermal microbiome was unexpectedly diverse, and dominated by acidophilic and mesophilic sulfur- and iron-cycling bacteria, mercury- and arsenic-resistant bacteria, and thermophilic and acidophilic archaea. Integrating microbiome structure and metagenomic potential with geochemical constraints, we constructed a conceptual model for biogeochemical mercury cycling in geothermal springs. The model includes abiotic and biotic controls on mercury speciation, and illustrates how geothermal mercury cycling may couple to microbial community dynamics and sulfur and iron biogeochemistry. IMPORTANCELittle is currently known about biogeochemical mercury cycling in geothermal systems. This manuscript presents an important new conceptual model, supported by genome-resolved metagenomic analysis and detailed geochemical measurements. This work provides a framework for studying natural geothermal mercury emissions globally. Specifically, our findings have implications for mercury speciation in wastewaters from geothermal power plants and the potential environmental impacts of microbially and abiotically formed mercury species, particularly where mobilized in spring waters that mix with surface- or ground-waters. Furthermore, in the context of thermophilic origins for microbial mercury volatilisation, this report yields new insights into how such processes may have evolved alongside microbial mercury methylation/demethylation, and the environmental constraints imposed by the geochemistry and mineralogy of geothermal systems.

microbiology↗