Showing papers in "Geomicrobiology Journal in 2011"
TL;DR: In this article, enrichment for indigenous microorganisms capable of hydrolyzing urea in the presence of CaCl2 was performed on potentially liquefiable saturated soils in both the laboratory and in situ.
Abstract: Enrichments for indigenous microorganisms capable of hydrolyzing urea in the presence of CaCl2 were performed on potentially liquefiable saturated soils in both the laboratory and in situ. Following enrichment, treatment of soils with nutrients, CaCl2 and urea resulted in significant in situ precipitation of calcite, even at depth, by indigenous microorganisms. The biomineralized soils showed properties that indicate calcite precipitation increased their resistance to seismic-induced liquefaction.
257 citations
TL;DR: In this paper, the U.S. Department of Energy's Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, has demonstrated that uranium concentrations in groundwater can be decreased to levels below the EPA's drinking water standard (0.126 μM).
Abstract: Field biostimulation experiments at the U.S. Department of Energy's Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, have demonstrated that uranium concentrations in groundwater can be decreased to levels below the U.S. Environmental Protection Agency's (EPA) drinking water standard (0.126 μM). During successive summer experiments – referred to as “Winchester” (2007) and “Big Rusty” (2008) - acetate was added to the aquifer to stimulate the activity of indigenous dissimilatory metal-reducing bacteria capable of reductively immobilizing uranium. The two experiments differed in the length of injection (31 vs. 110 days), the maximum concentration of acetate (5 vs. 30 mM), and the extent to which iron reduction (“Winchester”) or sulfate reduction (“Big Rusty”) was the predominant metabolic process. In both cases, rapid removal of U(VI) from groundwater occurred at calcium concentrations (6 mM) and carbonate alkalinities (8 meq/L) where Ca-UO2-CO3 ternary complexes constitute >90% of uranyl ...
236 citations
TL;DR: The results suggest that, although the potential electron acceptors in sulfate-depleted habitats remain elusive, the niche separation of ANME-1 and -2 may be controlled by in situ concentration of sulfate and the availability in sediments.
Abstract: In this study, we investigated the diversity and spatial distribution of anaerobic methanotrophic archaea (ANMEs) in sediments of a gas hydrate field off Joetsu in the Japan Sea. Distribution of ANMEs in sediments was identified by targeting the gene for methyl coenzyme M reductase alpha subunit (mcrA), a phylogenetically conserved gene that occurs uniquely in methanotrophic and methanogenic archaea, in addition to 16S rRNA genes. Quantitative PCR analyses of mcrA genes in 14 piston core samples suggested that members of ANME-1 group would dominate AOM communities in sulfate-depleted sediments, even below the sulfate-methane interface, while ANME-2 archaea would prefer to populate in shallower sediments containing comparatively higher sulfate concentrations. These results suggest that, although the potential electron acceptors in sulfate-depleted habitats remain elusive, the niche separation of ANME-1 and -2 may be controlled by in situ concentration of sulfate and the availability in sediments.
71 citations
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TL;DR: Fungal interactions with uranium are relevant to the biogeochemistry of uranium, but also to the applied area of bioremediation as discussed by the authors. But it is not fully established whether fungi are capable of U(VI) reductive immobilization.
Abstract: Free-living and symbiotic fungi can interact with, and transform certain uranium species, while general metabolic activities such as decomposition of organic substances and dissolution of rocks and minerals may result in products that indirectly react with uranium. Excretion of organic acids is an important property of many fungi which can result in U-complex formation and U-ore dissolution for example, while fungal biomass can act as an efficient U biosorbent and surface/matrix for U crystallization and biomineralization. Secondary products of organic matter decomposition and mineral dissolution may result in secondary U-complex and U-mineral formation. It is not fully established whether fungi are capable of U(VI) reductive immobilization. Fungal interactions with uranium are relevant to the biogeochemistry of uranium, but also to the applied area of bioremediation. While U biosorption seems not to have a commercial future, some fungal activities may have relevance to contaminated terrestrial habitats. ...
62 citations
TL;DR: In this paper, a field-scale experiment was conducted to evaluate organic carbon amendment of mine tailings as a technique for pore water and drainage treatment, and six test cells were constructed by amending sulfid...
Abstract: A field-scale experiment was conducted to evaluate organic carbon amendment of mine tailings as a technique for pore water and drainage treatment. Six test cells were constructed by amending sulfid ...
53 citations
TL;DR: Community analysis as well as the environmental conditions and the metabolites detected in a previous study are consistent with the following scenario of methane release: Weathering of coal and timber is initiated by wood-degrading Fungi and Bacteria under a suboxic atmosphere.
Abstract: Worldwide, abandoned coal mines release substantial amounts of methane, which is largely of biogenic origin. The aim of this study was to understand the microbial processes involved in mine-gas formation. Therefore, coal and timber samples and anaerobic enrichments from two abandoned coal mines in Germany were subjected to DGGE analyses and quantitative PCR. The primers used were specific for Bacteria, Archaea, Fungi, and the key functional genes for sulfate reduction (dsrA) and methanogenesis (mcrA). A broad spectrum of facultative anaerobic bacteria and acetogens belonging to all five groups (α-ϵ) of the Proteobacteria, as well as the Bacteroidetes, Tenericutes, Actinobacteria, Chlorobi and Chloroflexi were detected. Archaea were represented by acetoclastic Methanosarcinales and Crenarchaeota with an unknown metabolism. Fungi formed thick biofilms particularly on timber, and were identified as typical wood degraders belonging to the Ascomycetes and Basidiomycetes. The community analysis as well as the e...
50 citations
TL;DR: In this article, the authors showed that hollandite is a good catalyst for oxygen evolution in presence of cerium (IV) ammonium nitrate or tris (2,2′-bipyridyl)ruthenium (III).
Abstract: Oxygen evolution was observed upon mixing either hollandite, which has been proposed as a structural model for the biological water oxidizing complex, or hausmannite with an aqueous solution of cerium (IV) ammonium nitrate. Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding either hollandite or hausmannite to an aqueous solution containing tris (2,2′-bipyridyl)ruthenium(II) chloride and chloro pentaammine cobalt(III) chloride in acetate buffer. These experiments showed that hollandite is a good catalyst for oxygen evolution in presence of cerium (IV) ammonium nitrate or tris (2,2′-bipyridyl)ruthenium (III). Thus, hollandite is not only a structural but also a functional model for the biological water oxidizing complex. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental file.
49 citations
TL;DR: The deeper aquifer showed higher abundance of aerobic bacterial populations including the presence of iron-oxidizing Sideroxydans possibly of importance for the sorption of arsenic on oxidized iron hydroxides, which may provide information on suitable conditions for arsenic immobilization useful for future bioremediation efforts.
Abstract: At Titas, Bangladesh, two aquifers of different arsenic concentrations and redox conditions were investigated to link variations in geochemistry to in situ bacterial diversity characterized by T-RFLP (terminal restriction fragment length polymorphism) and clone library analysis. While the shallow aquifer was characterized by reduced gray sediments with a higher share of easily mobilized sedimentary arsenic (2.6% was easily mobilized from 18 mg/kg of total arsenic available in sediments) and higher aqueous arsenic concentrations of 120 ± 6 μg/L (45% arsenite), the deeper aquifer consisted of brown oxidized sediments with lower aqueous arsenic concentrations, predominantly as arsenate (60 ± 6 μg/L; 3% arsenite) and a higher share of tightly bound arsenic (only 0.6% of 53 mg/kg total sorbed arsenic was easily mobilized). The bacterial communities of both aquifers were dominated by putative aerobic or denitrifying populations of Pseudomonas, Elizabethkingia and Pantoea. The shallow aquifer was more diverse in...
47 citations
TL;DR: The millimetric penetration of MCF strains within silicate and carbonate lithotypes was quantified and the influence of petrographic features in determining hyphal passageways satisfies a model of physical penetration during the early stages of colonization.
Abstract: Physicochemical deterioration processes driven by lithobiontic microcolonial fungi (MCF) and endolithic lichens (EL) are still mostly unresolved. Here, the millimetric penetration of MCF strains within silicate and carbonate lithotypes was quantified. The influence of petrographic features in determining hyphal passageways satisfies a model of physical penetration during the early stages of colonization, already described for EL. The MCF and EL secretion of iron-chelating metabolites accounts for iron mobilization in desert-varnish formation, often putatively related to fungal colonization. Increased dissolution of limestone by the model iron chelator desferrioxamine indicates the possible involvement of these MCF and EL secretes in pitting carbonates.
45 citations
TL;DR: In this article, the relative importance of enzymatic vs. abiotic U(VI) reduction mechanisms and the long-term fate of U(IV) was assessed using sediment microcosm and Fe(II)-bearing biomineral experiments.
Abstract: Under anaerobic conditions, uranium solubility is significantly controlled by the microbially mediated reduction of relatively soluble U(VI) to poorly soluble U(IV). However, the reaction mechanism(s) for bioreduction are complex with prior sorption of U(VI) to sediments significant in many systems, and both enzymatic and abiotic U(VI) reduction pathways potentially possible. Here, we describe results from sediment microcosm and Fe(II)-bearing biomineral experiments designed to assess the relative importance of enzymatic vs. abiotic U(VI) reduction mechanisms and the long-term fate of U(IV). In oxic sediments representative of the UK Sellafield reprocessing site, U(VI) was rapidly and significantly sorbed to surfaces and during microbially-mediated bioreduction, XAS analysis showed that sorbed U(VI) was reduced to U(IV) commensurate with Fe(III)-reduction. Additional control experiments with Fe(III)-reducing sediments that were sterilized after bioreduction and then exposed to U(VI), indicated that U(VI) ...
44 citations
TL;DR: The Integrated Field Research Challenge site in Oak Ridge, Tennessee provides an ideal location to address the challenges nitrate poses to uranium bioreduction as the site encompasses several different geochemical conditions as discussed by the authors.
Abstract: Mining and enrichment of uranium (U) for nuclear weapons and energy has left this radionuclide an important groundwater contaminant in the United States and worldwide. The use of nitric acid in these processes has also resulted in low pH and high nitrate concentrations in U-contaminated subsurface sediments. This presents problems for bioremediation strategies to control the migration of U in groundwater, usually achieved through microbial reduction of soluble U(VI) to insoluble U(IV) upon electron donor addition to the subsurface. Nitrate, which serves as a competitive electron acceptor in the subsurface, can inhibit or retard U(VI) reduction efforts; as well, intermediates of nitrate respiration (or denitrification), such as nitrite, can lead to U(IV) oxidation and remobilization. The Integrated Field Research Challenge site in Oak Ridge, Tennessee provides an ideal location to address the challenges nitrate poses to uranium bioreduction as the site encompasses several different geochemical conditions: ...
TL;DR: In this paper, a comparative analysis of the superficial bacterial and archaeal community structure of multiple stalactites from two different cave formations located in close proximity to each other in a nonhuman-impacted area of Kartchner Caverns, Arizona, USA is presented.
Abstract: Information concerning the bacterial and archaeal communities present on calcite speleothems in carbonate caves is of interest because the activity of these microbes has been implicated as a potential biogenic component in the formation of secondary mineral deposits. In addition, these speleothems may harbor unique, previously unidentified microbes. The current study presents a comparative analysis of the superficial bacterial and archaeal community structure of multiple stalactites from two different cave formations located in close proximity to each other in a nonhuman-impacted area of Kartchner Caverns, Arizona, USA. PCR-denaturing gradient gel electrophoresis analysis (PCR-DGGE) revealed that microbial communities sampled from stalactites of a single speleothem are more similar to each other than to the communities sampled from stalactites of an adjacent speleothem, suggesting that both bacterial and archaeal communities are speleothem-specific. SR-XRD analysis confirmed that both speleothems sampled ...
TL;DR: In this paper, the authors examined the impact of speciation changes induced by dissolved Ca on the extent and rate of reduction of U(VI) in anaerobic environments, and examined the effect of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction.
Abstract: Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO2 2+ and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO2. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h ...
TL;DR: In vitro culture experiments confirmed the capability of many of the isolated strains to precipitate calcite and some of the identified isolates belonged to the Bacillus sp.
Abstract: Moonmilk, a microcrystalline secondary cave deposit, actively forms on the floor of Krem Mawmluh - a limestone cave in Meghalaya, Northeastern India. Due to the abundance of micrite and calcified m ...
TL;DR: In this paper, the cell-radionuclide interactions of two bacterial species (i.e., Shewanella putrefaciens and Desulfovibrio aespoeensis) with Cm, Pm, and Pu were investigated in vitro and the results were found to agree with literature data.
Abstract: This review summarizes research into interactions between microorganisms and radionuclides under conditions typical of a repository for high-level radioactive waste in deep hard rock environments at a depth of approximately 500 m. The cell–radionuclide interactions of strains of two bacterial species (i.e., Shewanella putrefaciens and Desulfovibrio aespoeensis) with Cm, Pm, and Pu were investigated in vitro and the results were found to agree with literature data. Siderophores are capable of binding actinides strongly and need to be considered in terms of radionuclide mobility in the subsurface. Siderophores and other bioligands were found to have a generally very strong mobilizing effect on Am, Cm, Fe, Np, Pm, Pu, Th, and U. Where reduced groundwater enters an aerobic environment, such as a large open fracture or fracture zone (e.g., in tunnels), there is the possibility of rapid aerobic bacterial metabolism, microbial proliferation, biofilm development, and iron oxide formation. In these environments, t...
TL;DR: Thermodynamic analyses indicate that methanogenic reactions are inhibited by the high partial pressure of abiogenic CH4 and that sulfate-reducing reactions are more favorable, which is consistent with the abundance of 16S rRNA genes belonging to known sulfate reducing bacteria.
Abstract: The diversity of planktonic microorganisms in fluids from a group of flowing subterranean boreholes was monitored from the day they were drilled to as long as three and a half months after drilling as they drained into Evander Au mine. Geochemical analyses of the water, characterization of microbial communities by phospholipids fatty acid (PLFA) and DNA sequence analyses, and calculations of free energy flux indicated that mine-introduced microbial contaminants, dominated by β and γ Proteobacteria, Cenarchaeaceae and Candidatus Nitrososphaera, were flushed from the boreholes and replaced by fracture water derived microbial communities dominated by Firmicutes, Methanosarcinalesand Thermoproteaceaea. The fracture water was a mixture of paleometeoric water and 2.0 Ga old, diagenetically altered, hydrothermal fluid. The C and H isotopic data for C1−4 indicated that the CH4 was primarily abiogenic in origin although ∼35–50% of it might have originated from microbial methanogenesis. Noble gas analyses yielded e...
TL;DR: In this article, the authors evaluated the relationship between the abiotic conditions and the lichen growth form in the Negev and found a correlation between dew duration and the combined duration of dew and rain (r2 = 0.79).
Abstract: Dew and rain were measured along the north facing slope (NFS, with epilithic lichens predominating) and the south-facing slope (SFS, with endolithic lichens predominating) in the Negev (P = 95 mm) in order to evaluate the relationships between the abiotic conditions and the lichen growth form. Although insignificant differences characterize the rain and dew amounts with the epilithic growth form, high correlation was obtained between dew duration (r2 = 0.73) and the combined duration of dew and rain (r2 = 0.79). The data imply that daylight wetness duration rather than the amount of precipitation may explain the predominance of epilithic lichens at the shaded NFS.
TL;DR: In this article, the ability of wetland bacteriogenic iron oxides (BIOS) to immobilize iodide in contaminated groundwater systems near Chalk River, Canada was investigated using an autotitrator and an I− ion-selective electrode to generate high-resolution anion sorption data over a pH range of 2.5 to 9.5.
Abstract: This study was performed to determine the ability of wetland bacteriogenic iron oxides (BIOS) to immobilize iodide in contaminated groundwater systems near Chalk River, Canada. The sorption of iodide onto synthetic hydrous ferric oxide (HFO) and BIOS was investigated using an autotitrator and an I− ion-selective electrode to generate high-resolution anion sorption data over a pH range of 2.5 to 9. The effect of strontium sorption in the presence of I− was also investigated to determine its effect on iodide retention as it is also a common contaminant near Chalk River. Both HFO and BIOS correspond to 2-line ferrihydrite with surface areas of 227.7 m2 g−1 and 92.52 m2 g−1, respectively. Sorption of I− was found to be pH dependent for both HFO and BIOS and was most strongly immobilized at pH 2.5. The pH at which 50% of the I− was bound to HFO occurred at pH 4.0, whereas BIOS maintained 50% sorption to pH 9. Field data also indicated a 54% decrease for iodine and 75% for 129I in waters passing over in-situ BI...
TL;DR: In this paper, an aragonite travertine at Nagano-yu hot spring, SW Japan, exhibits clear sub-millimeter-order lamination that resembles ancient ministromatolites.
Abstract: An aragonite travertine at Nagano-yu hot spring, SW Japan, exhibits clear sub-millimeter-order lamination that resembles ancient ministromatolites. Thirty-three hours of continuous observation showed that the lamination is formed daily with no changes in physicochemical properties except light intensity. Phylotype analysis and fluorescence in situ hybridization indicate that Hydrogenophaga sp. is dominant and concentrated in diurnal layers containing abundant extracellular polymeric substances. Growth of Hydrogenophaga sp. is activated in the daytime, likely due to extracellular polymeric substance production by cyanobacterial photosynthesis. Daytime development of Hydrogenophaga-dominant biofilms, and the concurrent inhibiting effect on aragonite precipitation, explains the daily lamination observed.
TL;DR: The release of radioactive materials into the environment has been a subject of intense public concern and has led to substantial research activities into the environmental fate of key radionuclide as mentioned in this paper.
Abstract: The release of radioactive materials into the environment has been a subject of intense public concern and has led to substantial research activities into the environmental fate of key radionuclide...
TL;DR: Examination of physicochemical properties of the Laguna de la Piedra as well as the microbial diversity of the evaporite deposits of the Salar de Atacama finds a single phylotype of halophilic archaea and a oxytrichid ciliate.
Abstract: The Salar de Atacama, located in Northern Chile, is a wide salt flat that is characterized by several salt lakes, which are locally called lagunas. The Laguna de la Piedra is one of the salt lake systems that is located in the northernmost sector of the Salar de Atacama. The present paper examines some physicochemical properties of the Laguna de la Piedra as well as the microbial diversity of the evaporite deposits. Under extreme desiccation and ambient UV flux, the evaporite deposits can create favorable endolithic microniches for the development of microorganisms. In the Laguna de la Piedra these deposits host a variety of halophilic microorganisms, which were investigated by using an optical and environmental scanning electron microscope (ESEM) as well as molecular diversity studies based on the small subunit ribosomal (SSU) rRNA of Bacteria, Archaea and Eucarya. We detected a single phylotype of halophilic archaea and a oxytrichid ciliate. Within the bacteria, a variety of Cyanobacteria, Bacteroidetes...
TL;DR: The kinetics of uranium(VI) reduction by Shewanella oneidensis strain MR-1 was studied for varied pH and concentrations of dissolved inorganic carbon (DIC) and calcium as discussed by the authors.
Abstract: The kinetics of uranium(VI) reduction by Shewanella oneidensis strain MR-1 was studied for varied pH and concentrations of dissolved inorganic carbon (DIC) and calcium. These are key variables affecting U(VI) speciation in aqueous systems. For all conditions studied, a nearly log-linear decrease of [U(VI)] suggested pseudo–first-order kinetics with respect to U(VI). The reduction rate constants (k) decreased with increasing DIC and calcium concentration, and were sensitive to pH. A positive correlation was found between k and the logarithm of the total concentration of U(VI)-hydroxyl and U(VI)-organic complexes. Linear correlations of the rate constant with the redox potential (EH) of U(VI) reduction and the associated Gibbs free energy of reaction (Gr) were found for both Ca-free and Ca-containing systems. Both EH and Gr are strong functions of aqueous U(VI) speciation. Because the range in Gr among the experimental conditions was small, the differences in k are more likely to be due to differences in EH or to differences in individual rate constants of U(VI) species. Calculation of conditional reduction rate constants for the major groups of U(VI) complexes revealed highest constants for the combined groups of U(VI)-hydroxyl and U(VI)-organic species, lower rate constants for the U(VI)-carbonate group, and much lower constants for the Ca-U(VI)-carbonate group. Mechanistic explanations for these findings are discussed.
TL;DR: In this article, energy dispersive X-ray microanalysis and transmission electron microscopy were used to investigate heavy metal accumulation and partitioning by a statistically meaningful assortment of bacteria and colloidal minerals in metal-polluted lake sediment.
Abstract: Energy dispersive X-ray microanalysis and transmission electron microscopy were used to investigate heavy metal accumulation and partitioning by a statistically meaningful assortment of bacteria and colloidal minerals in metal-polluted lake sediment. Visually selected external and internal parts of bacterial cells were analysed individually. Variations in element distribution and relationships provided clues to small-scale biogeochemical processes and their implications for microbial ecology. Most bacteria had mineral coatings of varying composition and texture formed by adsorption of detrital clay and precipitation of authigenic oxides and clay attributable to Fe and Al complexing by cell walls and fibrils. Fe oxide precipitated abiotically and indiscriminately on bacteria and minerals, but Mn oxide was purely biogenic, precipitating only on certain bacteria. Cell walls also complexed Cu; formation of mineral coatings interfered with Cu binding, but the coatings themselves scavenged Cu. Cu and Zn were bo...
TL;DR: This study investigated the abundance and distribution of AOA and AOB in the production waters of high-temperature oil reservoirs by using real-time PCR and phylogenetic analysis based on amoA genes, and showed distribution of prokaryotic amoB gene in various oil reservoirs was affected by production processes.
Abstract: Although the presence and activity of ammonia-oxidation archaea (AOA) and ammonia-oxidation bacteria (AOB) were observed in thermophilic habitats recently, their existence in the geothermal subterranean oil reservoirs is still not available. This study investigated the abundance and distribution of AOA and AOB in the production waters of high-temperature oil reservoirs by using real-time PCR and phylogenetic analysis based on amoA genes. The results indicated the occurrence of both AOA and AOB in 9 out of totally 17 wells. The AOA-like phylotypes are mainly clustered within two major clades of archaeal amoA sequences known from water columns, sediments and soils: clusters A and B, and a few clones are related to the new genera: Candidatus ‘Nitrosocaldus yellowstonii’. The AOB-like phylotypes mainly belong to Nitrosospira and Nitrosomonas clusters, while two of them are deep-branched in Nitrosospira cluster and showed no substantial alignment to the known cultured AOB, indicating the possibility of new AOB...
TL;DR: In this article, results from both oxic adsorption and anaerobic microcosm experiments to examine the fate of sorbed U(VI) during microbially mediated bioreduction were presented.
Abstract: It is well known that microbially mediated reduction can result in the removal of U(VI)(aq) from solution by forming poorly soluble U(IV) oxides; however, the fate of U(VI) already associated with mineral surfaces is less clear. Here we describe results from both oxic adsorption and anaerobic microcosm experiments to examine the fate of sorbed U(VI) during microbially mediated bioreduction. The microcosm experiments contained sediment representative of the nuclear facility at Dounreay, UK. In oxic adsorption experiments, uptake of U(VI) was rapid and complete from artificial groundwater and where groundwater was amended with 0.2 mmol l−1 ethylenediaminetetraacetic acid (EDTA) a complexing ligand used in nuclear fuel cycle operations. By contrast, uptake of U(VI) was incomplete in groundwaters amended with 10 mmol l−1 bicarbonate. Analysis of sediments using X-ray adsorption spectroscopy showed that in these oxic samples, U was present as U(VI). After anaerobic incubation of U(VI) labelled sediments for 12...
TL;DR: In this paper, the effects of temperature (20, 30, and 40°C), pH (5.0, 7.0 and 9.0), and KNO3 concentration (0.001, 0.01, and 0.1 mol L−1) on Bacillus subtilis on three common minerals in soils such as kaolinite, montmorillonite and goethite under various environmental conditions.
Abstract: Adsorption of microorganisms on minerals is a ubiquitous interfacial phenomenon in soil. Knowledge of the extent and mechanisms of bacterial adsorption on minerals is of great agronomic and environmental importance. This study examined adsorption of Bacillus subtilis on three common minerals in soils such as kaolinite, montmorillonite and goethite under various environmental conditions. Isothermal titration calorimetry (ITC) was used to investigate the effects of temperature (20, 30, and 40°C), pH (5.0, 7.0, and 9.0) and KNO3 concentration (0.001, 0.01, and 0.1 mol L−1) on the adsorption by direct measurement of enthalpies. The results revealed that the adsorption process in all the mineral systems were exothermic, with the enthalpy changes (ΔHads ) ranging from −52 to −137, −33 to −147, and −53 to −141 kJ kg−1 (dry weight of adsorbed bacteria) for kaolinite, montmorillonite, and goethite, respectively. No obvious dependence of ΔHads on temperature was observed. The heat release for all the systems genera...
TL;DR: The organic phosphorus mineralizing bacteria (OPB) play an important role in phosphorus cycling in lake sediment, to which less attention has been paid as mentioned in this paper, and there existed a significant positive relationship between OPB numbers and alkaline phosphatase activities in the sediment.
Abstract: The organic phosphorus mineralizing bacteria (OPB) play an important role in phosphorus cycling in lake sediment, to which less attention has been paid. Monthly sediment samples in 2009 ending in October, together with the samples from different seasons (May, July, October, and December) in 2008, were collected at 6 sites in a Chinese large shallow eutrophic lake (Lake Taihu). The sediment OPB numbers ranged from 2.2 × 106 to 1.79 × 108 cells g−1 (dry weight) at different sampling sites and in different seasons, with the average being 3.88 × 107 cells g−1 (dry weight). Its number was highest at the most polluted site and peaked in spring and summer, which can be explained by the enrichment of organic matter in sediment. Furthermore, there existed a significant positive relationship between the OPB numbers and alkaline phosphatase activities in the sediment. The 6 OPB strains isolated from the sediment were distinct in terms of their colony morphology on the yolk agar, biochemical characteristics and phosp...
TL;DR: This discussion is focused on methanotrohphic bacterial population dynamics observed during growth on various copper species, to extrapolate their impact on geomicrobiological processes.
Abstract: Two distinct enzymatic pathways are implicated in the key step whereby methane is converted to methanol by the aerobic methane oxidizing bacteria (methanotrophs). These two enzymes, soluble and particulate methane monooxygenases (sMMO and pMMO, respectively), are evolutionarily unrelated. However, the activities of these enzymes are tightly linked to copper, which is central to the switch responsible for regulating MMO expression. When bioavailable copper exceeds a certain threshold relative to cell biomass, pMMO is expressed and its activity maintained by available copper. Below this threshold or when copper is entirely absent, sMMO catalyses methane oxidation. The individual forms of MMO degrade methane and hydrocarbon pollutants at different rates and efficiencies. Typically, pMMO is by up to 30% more efficient at methane degradation as opposed to sMMO which is more effective in the transformation of a wide range of hazardous hydrocarbons than pMMO. Consequently, the type of MMO expressed influences th...
TL;DR: The diversity, distribution and ecological significance of AOA in terrestrial hot springs in Kamchatka were explored using amoA genes complemented by analysis of Glycerol dialkyl glycerol tetraethers (GDGTs) of archaea, suggesting a spatial patterning of archaeal lipid biomarkers.
Abstract: Mounting evidence suggests that ammonia-oxidizing archaea (AOA) may play important roles in nitrogen cycling in geothermal environments. In this study, the diversity, distribution and ecological significance of AOA in terrestrial hot springs in Kamchatka (Far East Russia) were explored using amoA genes complemented by analysis of glycerol dialkyl glycerol tetraethers (GDGTs) of archaea. PCR amplification of functional genes (amoA) from AOA and ammonia-oxidizing bacteria (AOB) was performed on microbial mats/streamers and sediments collected from three hot springs (42°C to 87°C and pH 5.5-7.0). No amoA genes of AOB were detected. The amoA genes of AOA formed three distinct phylogenetic clusters with Cluster 3 representing the majority (∼59%) of OTUs. Some of the sequences from Cluster 3 were closely related to those from acidic soil environments, which is consistent with the predominance of low pH (<7.0) in these hot springs. Species richness (estimated by Chao1) was more frequently higher at temperatures ...
TL;DR: In this article, microbially induced carbonate dissolution was evaluated from sulfidic wells in the Edwards Aquifer, Texas, where filamentous biomass covers rock surfaces, with Gammaproteobacteria and Epsilonproteobacteria dominating the attached community.
Abstract: Microbially induced carbonate dissolution was evaluated from sulfidic wells in the Edwards Aquifer, Texas. Filamentous biomass covers rock surfaces, with Gammaproteobacteria and Epsilonproteobacteria dominating the attached community, but novel Alphaproteobacteria dominating the planktonic community. Despite fluids being saturated with respect to calcite, experimental calcite from in situ microcosms had significantly greater mass loss when colonized. Moreover, neoformed gypsum crystals were observed on colonized surfaces where fluids were undersaturated with respect to gypsum. The results are similar to findings from shallow cave and karst environments, and highlight the underappreciated role of microbes in the modification of carbonate aquifers and reservoirs.