Unlocking secrets of microbial ecotoxicology: recent achievements and future challenges.

Environmental pollution is one of the main challenges faced by humanity. By their ubiquity and vast range of metabolic capabilities, microorganisms are affected by pollution with consequences on their host organisms and on the functioning of their environment. They also play key roles in the fate of pollutants through the degradation, transformation, and transfer of organic or inorganic compounds.

Towards an understanding of the factors controlling bacterial diversity and activity in semi-passive Fe- and As-oxidizing bioreactors treating arsenic-rich acid mine drainage.

Semi-passive bioreactors based on iron and arsenic oxidation and coprecipitation are promising for the treatment of As-rich acid mine drainages. However, their performance in the field remains variable and unpredictable. Two bioreactors filled with distinct biomass carriers (plastic or a mix of wood and pozzolana) were monitored during 1 year.

Bio-precipitation of arsenic and antimony in a sulfate-reducing bioreactor treating real acid mine drainage water.

Arsenic (As) and antimony (Sb) from mining sites can seep into aquatic ecosystems by acid mine drainage (AMD). Here, the possibility of concomitantly removing As and Sb from acidic waters by precipitation of sulfides induced by sulfate-reducing bacteria (SRB) was investigated in a fixed-bed column bioreactor. The real AMD water used to feed the bioreactor contained nearly 1 mM As, while the Sb concentrations were increased (0.

Contrasting arsenic biogeochemical cycling in two Moroccan alkaline pit lakes.

Pit lakes resulting from the flooding of abandoned mines represent a valuable freshwater reserve. However, water contamination by toxic elements, including arsenic, compromises their use for freshwater supply. For a better management of these reserves, our aim was to gain insight into arsenic cycling in two Moroccan alkaline pit lakes.

In situ metabolic activities of uncultivated Ferrovum sp. CARN8 evidenced by metatranscriptomic analysis.

Amongst iron-oxidizing bacteria playing a key role in the natural attenuation of arsenic in acid mine drainages (AMDs), members of the Ferrovum genus were identified in mine effluent or water treatment plants, and were shown to dominate biogenic precipitates in field pilot experiments. In order to address the question of the in situ activity of the uncultivated Ferrovum sp. CARN8 strain in the Carnoulès AMD, we assembled its genome using metagenomic and metatranscriptomic sequences and we determined standardized expression values for protein-encoding genes.

Dynamics of Bacterial Communities Mediating the Treatment of an As-Rich Acid Mine Drainage in a Field Pilot.

Passive treatment based on iron biological oxidation is a promising strategy for Arsenic (As)-rich acid mine drainage (AMD) remediation. In the present study, we characterized by 16S rRNA metabarcoding the bacterial diversity in a field-pilot bioreactor treating extremely As-rich AMD , over a 6 months monitoring period. Inside the bioreactor, the bacterial communities responsible for iron and arsenic removal formed a biofilm ("biogenic precipitate") whose composition varied in time and space.

Hydraulic retention time affects bacterial community structure in an As-rich acid mine drainage (AMD) biotreatment process.

Arsenic removal consecutive to biological iron oxidation and precipitation is an effective process for treating As-rich acid mine drainage (AMD). We studied the effect of hydraulic retention time (HRT)-from 74 to 456 min-in a bench-scale bioreactor exploiting such process. The treatment efficiency was monitored during 19 days, and the final mineralogy and bacterial communities of the biogenic precipitates were characterized by X-ray absorption spectroscopy and high-throughput 16S rRNA gene sequencing.

Temperature and nutrients as drivers of microbially mediated arsenic oxidation and removal from acid mine drainage.

Microbial oxidation of iron (Fe) and arsenic (As) followed by their co-precipitation leads to the natural attenuation of these elements in As-rich acid mine drainage (AMD). The parameters driving the activity and diversity of bacterial communities responsible for this mitigation remain poorly understood. We conducted batch experiments to investigate the effect of temperature (20 vs 35 °C) and nutrient supply on the rate of Fe and As oxidation and precipitation, the bacterial diversity (high-throughput sequencing of 16S rRNA gene), and the As oxidation potential (quantification of aioA gene) in AMD from the Carnoulès mine (France).

Spatio-Temporal Detection of the Thiomonas Population and the Thiomonas Arsenite Oxidase Involved in Natural Arsenite Attenuation Processes in the Carnoulès Acid Mine Drainage.

The acid mine drainage (AMD) impacted creek of the Carnoulès mine (Southern France) is characterized by acid waters with a high heavy metal content. The microbial community inhabiting this AMD was extensively studied using isolation, metagenomic and metaproteomic methods, and the results showed that a natural arsenic (and iron) attenuation process involving the arsenite oxidase activity of several Thiomonas strains occurs at this site. A sensitive quantitative Selected Reaction Monitoring (SRM)-based proteomic approach was developed for detecting and quantifying the two subunits of the arsenite oxidase and RpoA of two different Thiomonas groups.

Diversity and Distribution of Arsenic-Related Genes Along a Pollution Gradient in a River Affected by Acid Mine Drainage.

Some microorganisms have the capacity to interact with arsenic through resistance or metabolic processes. Their activities contribute to the fate of arsenic in contaminated ecosystems. To investigate the genetic potential involved in these interactions in a zone of confluence between a pristine river and an arsenic-rich acid mine drainage, we explored the diversity of marker genes for arsenic resistance (arsB, acr3.

Diversity and geochemical structuring of bacterial communities along a salinity gradient in a carbonate aquifer subject to seawater intrusion.

In aquifers subject to saline water intrusion, the mixing zone between freshwater and saltwater displays strong physico-chemical gradients. Although the microbial component of these specific environments has been largely disregarded, the contribution of micro-organisms to biogeochemical reactions impacting water geochemistry has previously been conjectured. The objective of this study was to characterize and compare bacterial community diversity and composition along a vertical saline gradient in a carbonate coastal aquifer using high throughput sequencing of 16S rRNA genes.

Diversity and spatiotemporal dynamics of bacterial communities: physicochemical and other drivers along an acid mine drainage.

Deciphering the biotic and abiotic factors that control microbial community structure over time and along an environmental gradient is a pivotal question in microbial ecology. Carnoulès mine (France), which is characterized by acid waters and very high concentrations of arsenic, iron, and sulfate, provides an excellent opportunity to study these factors along the pollution gradient of Reigous Creek. To this end, biodiversity and spatiotemporal distribution of bacterial communities were characterized using T-RFLP fingerprinting and high-throughput sequencing.

Microbial ecology of arsenic-mobilizing Cambodian sediments: lithological controls uncovered by stable-isotope probing.

Microbially mediated arsenic release from Holocene and Pleistocene Cambodian aquifer sediments was investigated using microcosm experiments and substrate amendments. In the Holocene sediment, the metabolically active bacteria, including arsenate-respiring bacteria, were determined by DNA stable-isotope probing. After incubation with (13) C-acetate and (13) C-lactate, active bacterial community in the Holocene sediment was dominated by different Geobacter spp.

Genome Sequence of Hydrothermal Arsenic-Respiring Bacterium Marinobacter santoriniensis NKSG1T.

Marinobacter santoriniensis NKSG1(T) originates from metalliferous marine sediment. It can respire and redox cycle arsenic species and perform mixotrophic, nitrate-dependent Fe(II) oxidation. The genome sequence, reported here, will help further elucidate the genetic mechanisms underlying these and other potential biogeochemically relevant functions, such as arsenic and mercury resistance and hydrocarbon degradation.

Earthworm activity in a simulated landfill cover soil shifts the community composition of active methanotrophs.

Landfills represent a major source of methane in the atmosphere. In a previous study, we demonstrated that earthworm activity in landfill cover soil can increase soil methane oxidation capacity. In this study, a simulated landfill cover soil mesocosm (1 m × 0.

Monitoring of bacterial communities during low temperature thermal treatment of activated sludge combining DNA phylochip and respirometry techniques.

Sludge reduction is one of the major challenges in biological wastewater treatment. One approach is to increase the sludge degradation yield together with the biodegradation kinetics. Among the various sludge pretreatment strategies proposed, thermal pretreatment at around 65 °C was described as promising.

Marinobacter santoriniensis sp. nov., an arsenate-respiring and arsenite-oxidizing bacterium isolated from hydrothermal sediment.

A Gram-negative, arsenate-respiring and arsenite-oxidizing marine bacterium, NKSG1(T), was isolated from hydrothermal sediment at Santorini, Greece. Strain NKSG1(T) was a facultatively anaerobic, motile, non-spore-forming, rod-shaped bacterium. Growth occurred optimally at 35-40 degrees C, between pH 5.

Redox cycling of arsenic by the hydrothermal marine bacterium Marinobacter santoriniensis.

Marinobacter santoriniensis NKSG1(T) is a mesophilic, dissimilatory arsenate-reducing and arsenite-oxidizing bacterium isolated from an arsenate-reducing enrichment culture. The inoculum was obtained from arsenic-rich shallow marine hydrothermal sediment from Santorini, Greece, with evidence of arsenic redox cycling. Growth studies demonstrated M.

Effect of earthworms on the community structure of active methanotrophic bacteria in a landfill cover soil.

In the United Kingdom, landfills are the primary anthropogenic source of methane emissions. Methanotrophic bacteria present in landfill biocovers can significantly reduce methane emissions via their capacity to oxidize up to 100% of the methane produced. Several biotic and abiotic parameters regulate methane oxidation in soil, such as oxygen, moisture, methane concentration and temperature.

Effect of carbon and nitrogen input on the bacterial community structure of Neocaledonian nickel mine spoils.

Neocaledonian mine spoils are considered as an extreme environment because of their edaphic conditions, which are unfavourable for life. The principal characteristics of this soil are the high nickel content (20,000 ppm) and the very low carbon (0.2%) and nitrogen (0.

Nickel mine spoils revegetation attempts: effect of pioneer plants on two functional bacterial communities involved in the N-cycle.

Nickel mine spoils in New Caledonia represent an extreme environment, rich in nickel and strongly deficient in elementary elements such as carbon and nitrogen. To rehabilitate these sites, revegetation attempts are performed with endemic plant species establishing dinitrogen-fixation symbiosis (Gymnostoma webbianum and Serianthes calycina). As this biological fixation process provides the major source of available nitrogen in this extreme environment, it could be expected that nitrogen cycling would be stimulated.

Adaptation to nickel spiking of bacterial communities in neocaledonian soils.

Adaptation to nickel of bacterial communities of two extreme neocaledonian soils (an ultramafic soil and an acidic soil) was investigated by nickel spiking and compared with adaptation in a non-neocaledonian soil used as reference. Soil microcosms were amended with nickel chloride (NiCl2), and bacterial community structure was analysed with the ribosomal intergenic spacer analysis (RISA) technique. Then, bacterial populations that respond to nickel stress were identified by cloning and sequencing.