Efficient phosphate recovery as vivianite: Synergistic effect of iron minerals and microorganism

Vivianite is a promising phosphorus recovery solution that has the potential to simultaneously relieve the phosphorus shortage and phosphorus pollution. By producing vivianite, dissimilatory iron reducing bacteria may substantially enhance...

Optimization of Environmental Conditions for Microbial Stabilization of Uranium Tailings, and the Microbial Community Response

Uranium pollution in tailings and its decay products is a global environmental problem. It is of great significance to use economical and efficient technologies to remediate uranium-contaminated soil. In this study, the effects of pH, temperature, and inoculation volume on stabilization efficiency and microbial community response of uranium tailings were investigated by a single-factor batch experiment in the remediation process by mixed sulfate-reducing bacteria (SRB) and phosphate-solubilizing bacteria (PSB, Pantoea sp. grinm-12). The results showed that the optimal parameters of microbial stabilization by mixed SRB-PSB were pH of 5.0, temperature of 25°C, and inoculation volume of 10%. Under the optimal conditions, the uranium in uranium tailings presented a tendency to transform from the acid-soluble state to residual state. In addition, the introduction of exogenous SRB-PSB can significantly increase the richness and diversity of endogenous microorganisms, effectively maintain the reductive environment for the microbial stabilization system, and promote the growth of functional microorganisms, such as sulfate-reducing bacteria (Desulfosporosinus and Desulfovibrio) and iron-reducing bacteria (Geobacter and Sedimentibacter). Finally, PCoA and CCA analyses showed that temperature and inoculation volume had significant effects on microbial community structure, and the influence order of the three environmental factors is as follows: inoculation volume > temperature > pH. The outcomes of this study provide theoretical support for the control of uranium in uranium-contaminated sites.

Microbiologically Influenced Corrosion of Iron by Nitrate Reducing Bacillus Sp

Iron has played a crucial role in the human ecosystem currently in transportation, manufacturing, and infrastructure. Iron oxide is known as rust, usually the reddish-brown oxide formed by iron and oxygen reactions in moisture from water or air. Microbiologically influenced corrosion (MIC) is a significant problem to the economic damage, especially in industrial sectors and its direct presence with nitrate/iron-reducing bacteria. This paper aims to explore the MIC of iron by nitrate-reducing Bacillus sp. including the redox reaction occurs, microbiologically influenced corrosion, iron/nitrate-reducing and mechanisms of microbial iron/nitrate reduction.

Effects of Magnetic Minerals Exposure and Microbial Responses in Surface Sediment Across Bohai Sea

Extensive production and application of magnetic minerals produce significant amounts of magnetic wastes to the environment. These magnetic minerals exposure could affect microbial community composition and geographic distribution. Here, we reported magnetic susceptibility is involved in determining bacterial α-diversity and community composition in surface sediment across Bohai Sea. Environmental factors (explained 9.80%) played a larger role than spatial variables (explained 6.72%) in conditioning the bacterial community composition. Exposure of magnetite center may shape geographical distribution of five dissimilatory iron reducing bacteria (DIRB). Microbial iron reduction ability and electroactive activity in sediment close to magnetite center are stronger than those far away. Our study provides novel understanding for response of DIRB and electroactive bacteria to magnetic minerals exposure.

The Impact of Ecological Restoration on Biogeochemical Cycling and Mercury Mobilization in Anoxic Conditions on Former Mining Sites in French Guiana

Successive years of gold mining in French Guiana has resulted in soil degradation and deforestation leading to the pollution and erosion of mining plots. Due to erosion and topography, gold panning sites are submitted to hydromorphy during rainfall and groundwater increases. This original study focused on characterizing the impact of hydromorphic anaerobic periods on bio-geochemical cycles. We sampled soil from five rehabilitated sites in French Guiana, including sites with herbaceous vegetation and sites restored with fabaceous plants, Clitoria racemosa (Cli) mon-oculture, Acacia mangium (Aca) monoculture, Clitoria racemosa and Acacia mangium (Mix) bi-culture. We conducted mesocosm experiments where soil samples were incubated in anaerobic conditions for 35 days. To evaluate the effect of anaerobic conditions on biogeochemical cycles, we measured the following parameters related to iron-reducing bacteria and sulfate-reducing bacteria metabolism throughout the experiment: CO2 release, carbon dissolution, sulphide production and sulphate mobilization. We also monitored the solubilization of iron oxyhydroxides, manganese oxides, aluminum oxides and mercury in the culture medium. Iron-reducing bacteria (IRB) and sulfate-reducing bacteria (SRB) are described as the major players in the dynamics of iron, sulfur and metal elements including mercury in tropical environments. The results revealed two trends in these rehabilitated sites. In the Aca and Mix sites, bacterial iron-reducing activity coupled with manganese solubilization was detected with no mercury solubilization. In herbaceous sites, a low anaerobic activity coupled with sulphide production and mercury solubilization were detected. These results are the first that report the presence and activity of iron- and sulfate-reductive communities at rehabilitated mining sites and their interactions with the dynamics of metallic elements and mercury. These results report, however, the positive impact of ecological restoration of mining sites in French Guiana by reducing IRB and SRB activities, the potential mobility of mercury and its risk of transfer and methylation.

Modeling cometabolism of hexavalent chromium by iron reducing bacteria in tertiary substrate system

In this study, a bacterial strain Serratia sp. was employed for the reduction of synthetically prepared different concentration of Cr(VI) solution (10, 25, 40, 50 and 100 mg/L). Cometabolism study have been carried out in the binary substrate system as well as in the tertiary substrate system. The results revealed that when glucose was added as a co-substrate, at low Cr(VI) concentration, complete reduction was achieved followed by increased biomass growth, but when Cr(VI) concentration was increased to 100 mg/L, the reduction decline to 93%. But in presence of high carbon iron filings (HCIF) as co-substrate even at higher Cr(VI) concentration i.e. 100 mg/L, 100% reduction was achieved and the cell growth continued till 124 h. The study was illustrated via Monod growth kinetic model for tertiary substrate system and the kinetic parameters revealed that the HCIF and glucose combination showed least inhibition to hexavalent chromium reduction by Serratia sp.

Authigenic nanoscale magnetite within methanic marine sediments

<p>Magnetic studies of methanic sediments focus mainly on magnetic iron sulfide (greigite, 3C pyrrhotite) formation and magnetic iron oxide (magnetite, titanomagnetite) dissolution, which mainly result from the release of hydrogen sulfide during sulfate-driven anaerobic oxidation of methane. In some instances, authigenic fine-grained magnetite within methanic environments is recognized from magnetic parameters, but the mechanisms for explaining its occurrence remain unclear. We report a novel authigenic nanoscale magnetite source in methanic marine sediments. The magnetite occurs in large concentrations in multiple horizons in a 230-m long sediment core with gas hydrate-bearing intervals. In contrast to typical biogenic magnetite produced by magnetotactic bacteria and dissimilatory iron-reducing bacteria, most particles have sizes of 200-800 nm and many are aligned in distinctive structures that resemble microbial precipitates. This new type of magnetite is interpreted to be a by-product of microbial iron reduction within methanic sediments. It will record younger paleomagnetic signals than surrounding sediments, which is important for paleomagnetic interpretations in methanic sediments.</p>