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Aqueous speciation modeling can be applied in predicting the rate of nitrilotriacetate (NTA) degradation by NTA monooxygenase for complex systems containing multiple species. This was gleaned from an investigation of the impact of aqueous speciation of NTA on enzymatic degradation. Results indicate that the rate of transport into the cell limits the biodegradation of various metal-NTA complexes and that NTA-Mo may be useful for degradaing NTA-metal complexes which are resistant to degradation by whole cells.

A study was conducted on the effect of nitrilotriacetic acid (NTA) aqueous speciation on the acid's biodegradation. The NTA degrading bacterium Chelatobacter heintzii was used in batch experiments to test the hypothesis that NTA-complexing metals having larger thermodynamic stability constants degrade at a slower pace compared with NTA complexes having metals with smaller stability constants. The degradability of the metal-NTA complexes was observed to be linked to their lability or relative rates of formation of HNTA2-.

Because microbes cannot be eliminated from radioactive waste disposal facilities, the consequences of bio-colonization must be understood. At a pre-Viking era vitrified hillfort, Broborg, Sweden, anthropogenic glass has been subjected to bio-colonization for over 1,500 years. Broborg is used as a habitat analogue for disposed radioactive waste glass to inform how microbial processes might influence long-term glass durability. Electron microscopy and DNA sequencing of surficial material from the Broborg vitrified wall, adjacent soil, and general topsoil show that the ancient glass supports a niche microbial community of bacteria, fungi, and protists potentially involved in glass alteration. Communities associated with the vitrified wall are distinct and less diverse than soil communities. The vitrified niche of the wall and adjacent soil are dominated by lichens, lichen-associated microbes, and other epilithic, endolithic, and epigeic organisms. These organisms exhibit potential bio-corrosive properties, including silicate dissolution, extraction of essential elements, and secretion of geochemically reactive organic acids, that could be detrimental to glass durability. However, long-term biofilms can also possess a homeostatic function that could limit glass alteration. This study documents potential impacts that microbial colonization and niche partitioning can have on glass alteration, and subsequent release of radionuclides from a disposal facility for vitrified radioactive waste. [ABSTRACT FROM AUTHOR]

Modern live-cell imaging approaches permit real-time visualization of biological processes, yet limitations exist for unicellular organism isolation, culturing, and long-term imaging that preclude fully understanding how cells sense and respond to environmental perturbations and the link between single-cell variability and whole-population dynamics. Here, we present a microfluidic platform that provides fine control over the local environment with the capacity to replace media components at any experimental time point, and provides both perfused and compartmentalized cultivation conditions depending on the valve configuration. The functionality and flexibility of the platform were validated using both bacteria and yeast having different sizes, motility, and growth media. The demonstrated ability to track the growth and dynamics of both motile and non-motile prokaryotic and eukaryotic organisms emphasizes the versatility of the devices, which should enable studies in bioenergy and environmental research. [ABSTRACT FROM AUTHOR]

Increasing concentrations of H2 with depth were observed across a geologic unconformity and associated redox transition zone in the subsurface at the Hanford Site in south-central Washington, USA. An opposing gradient characterized by decreasing O2 and nitrate concentrations was consistent with microbial-catalysed biogeochemical processes. Sterile sand was incubated in situ within a multilevel sampler placed across the redox transition zone to evaluate the potential for Tc( VII) reduction and for enrichment of H2-oxidizing denitrifiers capable of reducing Tc( VII). H2-driven TcO4− reduction was detected in sand incubated at all depths but was strongest in material from a depth of 17.1 m. A cidovorax spp. were isolated from H2-nitrate enrichments from colonized sand from 15.1 m, with one representative, strain JHL-9, subsequently characterized. JHL-9 grew on acetate with either O2 or nitrate as electron acceptor (data not shown) and on medium with bicarbonate, H2 and nitrate. JHL-9 also reduced pertechnetate ( TcO4−) under denitrifying conditions with H2 as the electron donor. H2-oxidizing A cidovorax spp. in the subsurface at Hanford and other locations may contribute to the maintenance of subsurface redox gradients and offer the potential for Tc( VII) reduction. [ABSTRACT FROM AUTHOR]

Bacteria from the C hloroflexi phylum are dominant members of phototrophic microbial mat communities in terrestrial thermal environments. Vitamins of B group are key intermediates (precursors) in the biosynthesis of indispensable enzyme cofactors driving numerous metabolic processes in all forms of life. A genomics-based reconstruction and comparative analysis of respective biosynthetic and salvage pathways and riboswitch regulons in over 20 representative C hloroflexi genomes revealed a widespread auxotrophy for some of the vitamins. The most prominent predicted phenotypic signature, auxotrophy for vitamins B1 and B7 was experimentally confirmed for the best studied model organism C hloroflexus aurantiacus. These observations along with identified candidate genes for the respective uptake transporters pointed to B vitamin cross-feeding as an important aspect of syntrophic metabolism in microbial communities. Inferred specificities of homologous substrate-binding components of ABC transporters for vitamins B1 ( ThiY) and B2 ( RibY) were verified by thermofluorescent shift approach. A functional activity of the thiamine-specific transporter ThiXYZ from C. aurantiacus was experimentally verified by genetic complementation in E . coli. Expanding the integrative approach, which was applied here for a comprehensive analysis of B-vitamin metabolism in C hloroflexi would allow reconstruction of metabolic interdependencies in microbial communities. [ABSTRACT FROM AUTHOR]

Geologic carbon dioxide (CO2) sequestration drives physical and geochemical changes in deep subsurface environments that impact indigenous microbial activities. The combined effects of pressurized CO2 on a model sulfate-reducing microorganism, Desulfovibrio vulgaris, have been assessed using a suite of genomic and kinetic measurements. Novel high-pressure NMR time-series measurements using 13C-lactate were used to track D. vulgaris metabolism. We identified cessation of respiration at CO2 pressures of 10 bar, 25 bar, 50 bar, and 80 bar. Concurrent experiments using N2 as the pressurizing phase had no negative effect on microbial respiration, as inferred from reduction of sulfate to sulfide. Complementary pressurized batch incubations and fluorescence microscopy measurements supported NMR observations, and indicated that non-respiring cells were mostly viable at 50 bar CO2 for at least 4 h, and at 80 bar CO2 for 2 h. The fraction of dead cells increased rapidly after 4 h at 80 bar CO2. Transcriptomic (RNA-Seq) measurements on mRNA transcripts from CO2-incubated biomass indicated that cells up-regulated the production of certain amino acids (leucine, isoleucine) following CO2 exposure at elevated pressures, likely as part of a general stress response. Evidence for other poorly understood stress responses were also identified within RNA-Seq data, suggesting that while pressurized CO2 severely limits the growth and respiration of D. vulgaris cells, biomass retains intact cell membranes at pressures up to 80 bar CO2. Together, these data show that geologic sequestration of CO2 may have significant impacts on rates of sulfate reduction in many deep subsurface environments where this metabolism is a key respiratory process. [ABSTRACT FROM AUTHOR]

This study measured reductive solubilization of plutonium(IV) hydrous oxide (Pu(IV)O2·xH2O(am)) with hydrogen (H2) as electron donor, in the presence or absence of dissimilatory metal-reducing bacteria (DMRB), anthraquinone-2,6-disulfonate (AQDS), and ethylenediaminetetraacetate (EDTA). In PIPES buffer at pH 7 with excess H2, Shewanella oneidensis and Geobacter sulfurreducens both solubilized <0.001% of 0.5 mM Pu(IV)O2·xH2O(am) over 8 days, with or without AQDS. However, Pu(aq) increased by an order of magnitude in some treatments, and increases in solubility were associated with production of Pu(III)(aq). The solid phase of these treatments contained Pu(III)(OH)3(am), with more in the DMRB treatments compared with abiotic controls. In the presence of EDTA and AQDS, PuO2·xH2O(am) was completely solubilized by S. oneidensis and G. sulfurreducens in 24 h. Without AQDS, bioreductive solubilization was slower (~22 days) and less extensive (83-94%). In the absence of DMRB, EDTA facilitated reductive solubilization of 89% (without AQDS) to 98% (with AQDS) of the added PuO2·xH2O(am) over 418 days. An in vitro assay demonstrated electron transfer to PuO2·xH2O(am) from the S. oneidensis outer-membrane c-type cytochrome MtrC. Our results (1) suggest that PuO2·xH2O(am) reductive solubilization may be important in reducing environments, especially in the presence of complexing ligands and electron shuttles, (2) highlight the environmental importance of polynuclear, colloidal Pu, (3) provide additional evidence that Pu(III)-EDTA is a more likely mobile form of Pu than Pu(IV)-EDTA, and (4) provide another example of outer-membrane cytochromes and electron-shuttling compounds facilitating bioreduction of insoluble electron acceptors in geologic environments. [ABSTRACT FROM AUTHOR]

The fate of pertechnetate (99Tc(VII)O4-) during bioreduction was investigated in the presence of 2-line ferrihydrite (Fh) and various dissimilatory metal reducing bacteria (DMRB) (Geobacter, Anaeromyxobacter, Shewanella) in comparison with TcO4- bioreduction in the absence of Fh. In the presence of Fh, Tc was present primarily as a fine-grained Tc(IV)/Fe precipitate that was distinct from the Tc(IV)O2∙nH2O solids produced by direct biological Tc(VII) reduction. Aqueous Tc concentrations (<0.2 μm) in the bioreduced Fh suspensions (1.7 to 3.2 × 10-9 mol L-1) were over 1 order of magnitude lower than when TcO4- was biologically reduced in the absence of Fh (4.0 × 10-8 to 1.0 × 10-7 mol L-1). EXAFS analyses of the bioreduced Fh-Tc products were consistent with variable chain length Tc-O octahedra bonded to Fe-O octahedra associated with the surface of the residual or secondary Fe(III) oxide. In contrast, biogenic TcO2∙nH2O had significantly more Tc-Tc second neighbors and a distinct long-range order consistent with small particle polymers of TcO2. In Fe-rich subsurface sediments, the reduction of Tc(VII) by Fe(II) may predominate over direct microbial pathways, potentially leading to lower concentrations of aqueous 99Tc(IV). [ABSTRACT FROM AUTHOR]