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This research has investigated fungal transformations of rock phosphate (RP) by geoactive fungi, with particular emphasis on Aspergillus niger. Direct hyphal interaction with RP particles induced morphological and mineralogical changes, as revealed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The formation of the oxalate mineral calcium oxalate monohydrate (whewellite, CaC2O4·H2O) on RP surfaces showed that mycogenic oxalic acid was driving the chemical dissolution of apatite, with consequent phosphate release and secondary mineral formation. This was supported by abiotic testing of common fungal excreted organic acids which confirmed that oxalic acid was the only effective RP transforming agent and therefore responsible for the morphological and mineralogical changes observed in RP when exposed to fungal colonization. Cryogenic SEM provided evidence of fungal penetration and tunneling through RP particles demonstrating that physical interactions are also important for RP bioweathering, as well as biochemical mechanisms. These findings emphasize the important role of fungi in P cycling, with active participation in the transformation of mineral phosphates through physicochemical mechanisms and secondary oxalate biomineral formation. [ABSTRACT FROM AUTHOR]

Understanding the significance of plant-endophytic bacteria for bisphenol A (BPA) removal is of importance for any application of organic pollutant phytoremediation. In this research, Dracaena sanderiana with endophytic Pantoea dispersa showed higher BPA removal than uninoculated plants at 89.54 ± 0.88% and 79.08 ± 1.20%, respectively. Quantitative Real-Time PCR (qPCR) showed that P. dispersa increased from 3.93 × 107 to 8.80 × 107 16S rRNA gene copy number in root tissues from day 0 to day 5 which indicated that it could assist the plant in removing BPA during the treatment period. pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), conductivity, and salinity were reduced after 5 days of the experimental period. Particularly, BOD significantly decreased due to activities of the plants and microorganisms. Furthermore, an indigenous bacterial strain, Bacillus cereus NI, from the wastewater could remove BPA in high TDS and alkalinity condition of the wastewater. This work suggests that D. sanderiana plants could be used as a tertiary process in a wastewater treatment system and should be combined with its endophytic bacteria. In addition, B. cereus NI could also be applied for BPA removal from wastewaters with high TDS and salinity. [ABSTRACT FROM AUTHOR]

The bioleaching efficiency and mechanism of recovery of cobalt (Co) and nickel from laterites and pyritic ores by Aspergillus niger were investigated. Recoveries of Co from laterites and pyritic ores by direct bioleaching were 65.9 ± 1.8% and 4.9 ± 2.7%, respectively, while 30.9 ± 0.6% and 10.9 ± 6.2% recovery of Ni were obtained from laterites and pyritic ores, respectively. Recovery of Co via indirect bioleaching in the absence of the fungal biomass from laterite was significantly lower when compared with Co released by direct bioleaching. In the latter, hyphal penetration and colonization of the laterites were clearly observed by scanning electron microscopy (SEM). X-ray powder diffraction (XRPD) analysis of mineral phases before and after bioleaching indicated that cobalt-bearing goethite was the main phase bioleached in the laterites. No significant difference was found between Co recoveries from synthesized cobalt-bearing goethite by both direct and indirect bioleaching. Therefore, we propose that two processes are involved in bioleaching from laterites: (1) cobalt-bearing goethite was exposed via direct interactions between the fungus and the minerals and (2) cobalt-bearing goethite was dissolved by released metabolites of A. niger, such as organic acids. An incongruent pattern of Co and Fe bioleaching from the laterites was also a feature of the metal recovery process. [ABSTRACT FROM AUTHOR]

Metal and mineral transformations are a cornerstone of geomicrobiological processes. Of central importance are the mechanisms by which microorganisms alter the speciation and mobility of metals, including their properties of mineral dissolution or mineral formation. Such processes underpin natural biogeochemical cycles for metals, and related elements such as metalloids, and metal radionuclides, as well as those elements that may be commonly associated with metal compounds and minerals, e.g., P and S. They may also determine the fate of contaminant toxic metals and radionuclides when introduced or redistributed in the environment as a result of natural or anthropogenic activities. Such contamination is an increasing problem, and microbe-based systems are increasingly viewed as potentially useful approaches for bioremediation, as well as for element biorecovery. Biomineralization is a general term for the processes by which living organisms form minerals, and this can result in metal removal from solution providing a means of detoxification as well as biorecovery. Dead biota and derived products may also provide a template for mineral deposition, the reversibility, or otherwise, of the reaction depending on physico-chemical conditions. The most common biominerals precipitated by microbes include oxides, phosphates, sulfides and oxalates, and these can have special chemical properties such as high metal sorption capacities and redox catalysis. Furthermore, some biominerals may be deposited in nanoscale dimensions, providing further significant physical, chemical and biological properties of applied significance. The purpose of this Special Issue of theGeomicrobiology JournalonBiomineralization, Bioremediation and Biorecoveryis to bring together and highlight some specific examples of metal and radionuclide biomineralization by microorganisms from the different major microbial groups such as cyanobacteria, bacteria, microalgae and fungi. A range of elements and organisms are covered together with a variety of environmental and industrial contexts where a biomineralization approach may assist bioremediation, metal biorecovery or substrate stability. [ABSTRACT FROM AUTHOR]

Previous research has demonstrated the transformation of metallic lead into pyromorphite in solid and liquid medium by several species of fungi. In this work, the soil fungusPaecilomyces javanicuswas found to mediate formation of an unknown lead mineral phase after incubation in liquid media with lead shot. After 2 weeks' incubation, precipitated mineral phase particles were collected and X-ray powder diffraction (XRPD) revealed the presence of plumbonacrite (Pb10(CO3)6O(OH)6). After 4 weeks' incubation, the lead particles that accumulated inside the fungal pellets were transformed into a white lead-containing secondary mineral phase. Energy dispersive X-ray analysis (EDXA) and XRPD were used to attempt to identify the lead-containing secondary minerals produced. XRPD showed that lead oxalate (PbC2O4) and cerussite (PbCO3) were present as lead mineral species. However, another mineral phase was present that was not identifiable by XRPD. Fourier transform infrared spectroscopy (FTIR) identified hydroxyl (−OH) and carbonate (−CO32−) groups as the main functional groups within this unidentified secondary mineral phase. It was therefore concluded that this mineral phase is a new species of lead hydroxycarbonate. This is the first discovery of fungal-mediated formation of plumbonacrite and a new lead hydroxycarbonate, and therefore reveals a novel step in lead carbonation by fungi. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it asBacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium. [ABSTRACT FROM AUTHOR]

Sand storms have become a growing global environmental issue and there is an urgent need to explore cost-effective green technologies to stabilize the sands of desert regions. In this study, the performance of a ureolyticBacillussp. for stabilization of sands was evaluated. TheBacillussp. could efficiently consolidate sand particles by hydrolysis of urea and the subsequent production of calcite and aragonite minerals. The biostabilized sands had a high resistance to erosion by a 33 m s−1wind speed even after 12-d exposure to freeze-thaw cycles. The compressive strength of biostabilized sands was dependent on the applied cell density and concentrations of Ca2+and urea. High cell densities, urea and Ca2+concentrations reduced the compressive strength. The optimal cell density, Ca2+and urea concentrations were OD6000.4, 15 mM and 20 g L−1, respectively, when performance and cost were considered. This study shows that biostabilization of sand based on microbially induced carbonate precipitation (MICP) has potential for the prevention of sand storms and wind erosion of soil. [ABSTRACT FROM AUTHOR]

Acidithiobacillus ferrooxidansis a commonly used bacterial species for leaching gold ores to recover gold. The pH ofA. ferrooxidansbioleachates drastically changes from around 2.0 during bioleaching to about pH 8.0 as the cells are discharged together with the mine tailings containing high levels of Hg. It is not known how such a large pH shock would affect the properties of bacterial extracellular polymeric substances (EPS) and the transport of Hg in the mine tailings. In this study, the biochemical composition, molecular distribution, fluorescence properties and Hg(II) complexation by EPS ofA. ferrooxidanscultured at pH 2 and 8 were investigated. It was found that pH shock significantly altered the composition of EPS.A. ferrooxidansyielded more EPS under acid conditions than basic conditions. The acidic EPS contained more macromolecular proteins but less polysaccharide in comparison with the basic EPS. Phosphodiester functional groups in phospholipids and polysaccharides were found in the acidic EPS but not in the basic EPS. One tryptophan protein-like peak and one aromatic protein-like peak were identified in fluorescence spectra of the acidic EPS. Two aromatic protein-like peaks were identified from the fluorescence spectra of the basic EPS. The tryptophan protein-like substances in the acidic EPS interacted with Hg(II) and formed relatively stable complexes but with weak binding ability whereas the fluorescent aromatic protein-like substances in the acidic EPS did not bind Hg(II). However the aromatic protein-like substances in the basic EPS had a strong binding ability for Hg(II). The significant differences in composition and Hg complexation ability between EPS from acidic and basic environments indicate that a large pH shock during leaching of gold may exert a considerable impact on the behavior and fate of Hg in the mining areas. [ABSTRACT FROM AUTHOR]

Salinity and pH are two water chemical factors that vary drastically—seasonally or daily—in a variety of aquatic environments. Drastic change of salinity and pH may have a significant impact on adsorption of microbial extracellular polymers (EPS) to sediment minerals and thus influence many other important elemental geochemical processes. However, how salinity and pH changes affect EPS adsorption to minerals is poorly known. In the present study, adsorption of EPS from a hypersaline microbial mat to goethite at different pH values (4, 7 and 10) and salinity (0.15‰, 35‰ and 70‰) was monitored online using a quartz crystal microbalance (QCM) with EEM fluorescence spectroscopy as a complementary method. The adsorption kinetics were well described by an exponential function. The adsorption capacity of EPS to goethite significantly increased as the pH and salinity increased. The pH and salinity dependence of EPS adsorption to goethite is of great importance for understanding the environmental geochemistry of heavy metals in aquatic environments. In inland lakes and estuary zones, the seasonal or daily pulse of hydrological events will drastically alter water salinity and pH and consequently exert significant influences on the mobility, chemical species and ecotoxicity of heavy metals through the EPS pathway. It is necessary to systematically investigate the geochemical behavior of EPS in such dynamic aquatic environments and their potential effects on other geochemical processes. [ABSTRACT FROM AUTHOR]

Yeasts can exhibit various mechanisms that effect changes in metal speciation, toxicity and mobility. This research has examined the role of yeast phosphatases in lead bioprecipitation when utilizing an organic phosphorus-containing substrate as the sole phosphorus source. The formation of lead-containing biominerals after growth with organic phosphorus sources (glycerol 2-phosphate, phytic acid) was demonstrated and it was found that test yeasts were capable of mediating precipitation of lead phosphate (Pb3(PO4)2), pyromorphite (Pb5(PO4)3Cl), anglesite (PbSO4), and the lead oxides massicot and litharge (PbO), with variations in the mineral types produced between the different species. All test yeasts produced pyromorphite, and most produced anglesite. Lead oxides were only detected withPichia acacia. Lead-containing precipitates were also formed if yeast cells were pre-grown in organic-phosphorus-containing media and subsequently exposed to Pb(NO3)2. The role of phosphatases in mediating the formation of lead-containing minerals has provided further understanding of potential fungal roles in metal and mineral biogeochemistry as well as the possible significance of these mechanisms for element biorecovery or bioremediation. [ABSTRACT FROM AUTHOR]