18 research outputs found
Mechanism for microbial population collapse in a fluctuating resource environment.
Managing trade-offs through gene regulation is believed to confer resilience to a microbial community in a fluctuating resource environment. To investigate this hypothesis, we imposed a fluctuating environment that required the sulfate-reduce
Effects of calcium and phosphate on uranium(IV) oxidation: Comparison between nanoparticulate uraninite and amorphous U IV –phosphate
Enthalpies and Entropies of Cd and Zn Adsorption onto <i>Bacillus licheniformis</i> and Enthalpies and Entropies of Zn Adsorption onto <i>Bacillus subtilis</i> from Isothermal Titration Calorimetry and Surface Complexation Modeling
<div><p>Determining the thermodynamic driving force of metal-bacteria surface complexation is important for understanding why, from a thermodynamic perspective, these spontaneous reactions occur. We therefore determined the Gibbs energies, enthalpies, and entropies of Cd and Zn complexation onto <i>Bacillus licheniformis</i> and of Zn complexation onto <i>Bacillus subtilis</i> using surface complexation modeling and isothermal titration calorimetry. Our results indicated that Cd and Zn complexation onto <i>Bacillus licheniformis</i> is entropically driven at low pH and enthalpically driven at circumneutral pH. Zn complexation onto <i>Bacillus subtilis</i> is entropically driven, which suggests that <i>Bacillus licheniformis</i> has different donor ligands dominating reactivity around circumneutral pH.</p>
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Experimental study of the adsorption of an ionic liquid onto bacterial and mineral surfaces
Experimental Study of the Adsorption of an Ionic Liquid onto Bacterial and Mineral Surfaces
Thermodynamic Analysis of Nickel(II) and Zinc(II) Adsorption to Biochar
While numerous studies have investigated
metal uptake from solution
by biochar, few of these have developed a mechanistic understanding
of the adsorption reactions that occur at the biochar surface. In
this study, we explore a combined modeling and spectroscopic approach
for the first time to describe the molecular level adsorption of Ni(II)
and Zn(II) to five types of biochar. Following thorough characterization,
potentiometric titrations were carried out to measure the proton (H<sup>+</sup>) reactivity of each biochar, and the data was used to develop
protonation models. Surface complexation modeling (SCM) supported
by synchrotron-based extended X-ray absorption fine structure (EXAFS)
was then used to gain insights into the molecular scale metal–biochar
surface reactions. The SCM approach was combined with isothermal titration
calorimetry (ITC) data to determine the thermodynamic driving forces
of metal adsorption. Our results show that the reactivity of biochar
toward Ni(II) and Zn(II) directly relates to the site densities of
biochar. EXAFS along with FT-IR analyses, suggest that Ni(II) and
Zn(II) adsorption occurred primarily through proton-active carboxyl
(−COOH) and hydroxyl (−OH) functional groups on the
biochar surface. SCM-ITC analyses revealed that the enthalpies of
protonation are exothermic and Ni(II) and Zn(II) complexes with biochar
surface are slightly exothermic to slightly endothermic. The results
obtained from these combined approaches contribute to the better understanding
of molecular scale metal adsorption onto the biochar surface, and
will facilitate the further development of thermodynamics-based, predictive
approaches to biochar removal of metals from contaminated water
Key Metabolites and Mechanistic Changes for Salt Tolerance in an Experimentally Evolved Sulfate-Reducing Bacterium, Desulfovibrio vulgaris.
Rapid genetic and phenotypic adaptation of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough to salt stress was observed during experimental evolution. In order to identify key metabolites important for salt tolerance, a clone, ES10-5, which was isolated from population ES10 and allowed to experimentally evolve under salt stress for 5,000 generations, was analyzed and compared to clone ES9-11, which was isolated from population ES9 and had evolved under the same conditions for 1,200 generations. These two clones were chosen because they represented the best-adapted clones among six independently evolved populations. ES10-5 acquired new mutations in genes potentially involved in salt tolerance, in addition to the preexisting mutations and different mutations in the same genes as in ES9-11. Most basal abundance changes of metabolites and phospholipid fatty acids (PLFAs) were lower in ES10-5 than ES9-11, but an increase of glutamate and branched PLFA i17:1ω9c under high-salinity conditions was persistent. ES9-11 had decreased cell motility compared to the ancestor; in contrast, ES10-5 showed higher cell motility under both nonstress and high-salinity conditions. Both genotypes displayed better growth energy efficiencies than the ancestor under nonstress or high-salinity conditions. Consistently, ES10-5 did not display most of the basal transcriptional changes observed in ES9-11, but it showed increased expression of genes involved in glutamate biosynthesis, cation efflux, and energy metabolism under high salinity. These results demonstrated the role of glutamate as a key osmolyte and i17:1ω9c as the major PLFA for salt tolerance in D. vulgaris The mechanistic changes in evolved genotypes suggested that growth energy efficiency might be a key factor for selection.IMPORTANCE High salinity (e.g., elevated NaCl) is a stressor that affects many organisms. Salt tolerance, a complex trait involving multiple cellular pathways, is attractive for experimental evolutionary studies. Desulfovibrio vulgaris Hildenborough is a model sulfate-reducing bacterium (SRB) that is important in biogeochemical cycling of sulfur, carbon, and nitrogen, potentially for bio-corrosion, and for bioremediation of toxic heavy metals and radionuclides. The coexistence of SRB and high salinity in natural habitats and heavy metal-contaminated field sites laid the foundation for the study of salt adaptation of D. vulgaris Hildenborough with experimental evolution. Here, we analyzed a clone that evolved under salt stress for 5,000 generations and compared it to a clone evolved under the same condition for 1,200 generations. The results indicated the key roles of glutamate for osmoprotection and of i17:1ω9c for increasing membrane fluidity during salt adaptation. The findings provide valuable insights about the salt adaptation mechanism changes during long-term experimental evolution