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.

Characterization of plant growth promoting activities of indigenous bacteria of phosphate mine wastes, a first step toward revegetation.

Morocco holds the vast majority of the world's phosphate reserves, but due to the processes involved in extracting and commercializing these reserves, large quantities of de-structured, nutritionally deficient mine phosphate wastes are produced each year. In a semi-arid climate, these wastes severely hamper plant growth and development leading to huge unvegetated areas. Soil indigenous Plant Growth-Promoting Bacteria (PGPB) play a pivotal role in restauration of these phosphate mining wastes by revegetation, by increasing plants development, soil functioning, and nutrient cycling.

Description of Microbial Communities of Phosphate Mine Wastes in Morocco, a Semi-Arid Climate, Using High-Throughput Sequencing and Functional Prediction.

Soil microbiota are vital for successful revegetation, as they play a critical role in nutrient cycles, soil functions, and plant growth and health. A rehabilitation scenario of the abandoned Kettara mine (Morocco) includes covering acidic tailings with alkaline phosphate mine wastes to limit water infiltration and hence acid mine drainage. Revegetation of phosphate wastes is the final step to this rehabilitation plan.

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.

In-depth characterization of bacterial and archaeal communities present in the abandoned Kettara pyrrhotite mine tailings (Morocco).

In Morocco, pollution caused by closed mines continues to be a serious threat to the environment, like the generation of acid mine drainage. Mine drainage is produced by environmental and microbial oxidation of sulfur minerals originating from mine wastes. The fundamental role of microbial communities is well known, like implication of Fe-oxidizing and to a lesser extent S-oxidizing microorganism in bioleaching.

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 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.

Arsenic scavenging by aluminum-substituted ferrihydrites in a circumneutral pH river impacted by acid mine drainage.

Ferrihydrite (Fh) is a nanocrystalline ferric oxyhydroxide involved in the retention of pollutants in natural systems and in water-treatment processes. The status and properties of major chemical impurities in natural Fh is however still scarcely documented. Here we investigated the structure of aluminum-rich Fh, and their role in arsenic scavenging in river-bed sediments from a circumneutral river (pH 6-7) impacted by an arsenic-rich acid mine drainage (AMD).

Three-year survey of sulfate-reducing bacteria community structure in Carnoulès acid mine drainage (France), highly contaminated by arsenic.

A 3-year survey on sulfate-reducing bacteria (SRB) was conducted in the waters of the arsenic-rich acid mine drainage (AMD) located at Carnoulès (France) to determine the influence of environmental parameters on their community structure. The source (S5 station) exhibited most extreme conditions with pH lowering to ~1.2; iron, sulfate, and arsenic concentrations reaching 6843, 29 593, and 638 mg L(-1), respectively.

Predominance of aqueous Tl(I) species in the river system downstream from the abandoned Carnoulès mine (Southern France).

Thallium concentration reached up to 534 μg L(-1) in the Reigous acid mine drainage downstream from the abandoned Pb-Zn Carnoulès mine (Southern France). It decreased to 5.44 μg L(-1) in the Amous River into which the Reigous creek flows.

Characterization of the active bacterial community involved in natural attenuation processes in arsenic-rich creek sediments.

Acid mine drainage of the Carnoulès mine (France) is characterized by acid waters containing high concentrations of arsenic and iron. In the first 30 m along the Reigous, a small creek draining the site, more than 38% of the dissolved arsenic was removed by co-precipitation with Fe(III), in agreement with previous studies, which suggest a role of microbial activities in the co-precipitation of As(III) and As(V) with Fe(III) and sulfate. To investigate how this particular ecosystem functions, the bacterial community was characterized in water and sediments by 16S rRNA encoding gene library analysis.

Structure, function, and evolution of the Thiomonas spp. genome.

Bacteria of the Thiomonas genus are ubiquitous in extreme environments, such as arsenic-rich acid mine drainage (AMD). The genome of one of these strains, Thiomonas sp. 3As, was sequenced, annotated, and examined, revealing specific adaptations allowing this bacterium to survive and grow in its highly toxic environment.

Evaluation of protective effect of DNA vaccination with genes encoding antigens GRA4 and SAG1 associated with GM-CSF plasmid, against acute, chronical and congenital toxoplasmosis in mice.

To develop a multiantigenic vaccine against toxoplasmosis, two Toxoplasma gondii antigens, SAG1 and GRA4 selected on the basis of previous immunological and immunization studies, were chosen. We showed that DNA-based immunization with plasmids expressing GRA4 (pGRA4) or SAG1 (pSAG1mut) reduced mortality of susceptible C57BL/6 mice upon oral challenge with cysts of the 76K type II strain (62% survival). Immunization with pGRA4 and pSAG1mut, enhanced the protection (75% survival).

Arsenic oxidation and bioaccumulation by the acidophilic protozoan, Euglena mutabilis, in acid mine drainage (Carnoulès, France).

In the acid stream (pH 2.5-4.7) originating from the Carnoulès mine tailings, the acidophilic protozoan Euglena mutabilis grows with extremely high sulfate (1.

Bacterial formation of tooeleite and mixed arsenic(III) or arsenic(V)-iron(III) gels in the Carnoulès acid mine drainage, France. A XANES, XRD, and SEM study.

The oxidation of Fe(II) in acid mine drainage (AMD) leads to the precipitation of Fe(III) compounds which may incorporate toxic elements, such as arsenic (As), within their structure or adsorb them at their surface, thus limiting their mobility. The present work provides evidence for spatial and seasonal variations of microbial activity that influence arsenite oxidation and As immobilization in the heavily contaminated AMD from the Carnoulès mine, Gard, France ([As III] = 80 to 280 mg x L(-1) in the acidic spring draining the waste-pile). In the first tens of meters of the AMD, the rapid oxidation of Fe(II) leads to the coprecipitation of large amounts of As with Fe(III) in bacterial mats.

Bacterial immobilization and oxidation of arsenic in acid mine drainage (Carnoulès creek, France).

The acid waters (pH=2.73-3.37) originating from the Carnoulès mine tailings contain high dissolved concentrations of arsenic (1-3.