n situ EXAFS (extended X-ray absorption. ne structure), in situ XRD (X-ray diffraction) and electrochemical studies have been used to investigate the palladium hydride phases of carbon supported palladium nanoparticles as a function of applied potential. Electrochemical investigations showed an increase in the hydrogen to palladium ratio with an increasingly negative potential. The H/Pd ratio could be divided into four distinct regions, which described the palladium hydride phase present; the alpha-phase, a mixture of the alpha- and beta-phases, the beta-phase, and a hyperstoichiometric region. The beta-hydride phase stoichiometry obtained from the electrochemical data corresponded to PdH. However, the composition obtained from the lattice expansions observed from the in situ EXAFS and XRD, 3.3% and 3.8%, correspond to compositions of PdH0.59 to PdH0.68. The excess hydrogen and hyperstoichiometric amounts found at more negative potentials are attributed to either spillover on to the carbon support or trapping and subsequent reoxidation of H-2 in the porous electrode structure

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Aims:  Shanyin County is one of the most severe endemic arsenism affected areas in China but micro‐organisms that potentially release arsenic from sediments to groundwater have not been studied. Our aim was to identify bacteria with the potential to metabolize or transform arsenic in the sediments. Methods and Results:  Culture and nonculture‐based molecular methods were performed to identify arsenite‐oxidizing bacteria, arsenate‐reducing bacteria and arsenite oxidase genes. Arsenite‐oxidizing bacteria were identified only from the land surface to 7 m underground that were affiliated to α‐ and β‐Proteobacteria. Arsenate‐reducing bacteria were found in almost all the sediment samples with different depths (0–41 m) and mainly belong to γ‐Proteobacteria. Several novel arsenite oxidase genes (aoxBs) were identified from the upper layers of the sediments (0–7 m) and were found to be specific for arsenite‐oxidizing bacteria. Conclusions:  The distribution of arsenite‐oxidizing bacteria in upper layers and arsenate‐reducing bacteria in different depths of the sediments may impact the arsenic release into the nearby tubewell groundwater. Significance and Impact of the Study:  This study provides valuable sources of micro‐organisms (and genes) that may contribute to groundwater arsenic abnormality and may be useful to clean arsenic contaminated groundwater.

Genetic diversity is a result of evolution, enabling multiple ways for one particular physiological activity. Here, we introduce this strategy into bioengineering. We design two hydroxytyrosol biosynthetic pathways using tyrosine as substrate. We show that the synthetic capacity is significantly improved when two pathways work simultaneously comparing to each individual pathway. Next, we engineer flavin-dependent monooxygenase HpaBC for tyrosol hydroxylase, tyramine hydroxylase, and promiscuous hydroxylase active on both tyrosol and tyramine using directed divergent evolution strategy. Then, the mutant HpaBCs are employed to catalyze two missing steps in the hydroxytyrosol biosynthetic pathways designed above. Our results demonstrate that the promiscuous tyrosol/tyramine hydroxylase can minimize the cell metabolic burden induced by protein overexpression and allow the biosynthetic carbon flow to be divided between two pathways. Thus, the efficiency of the hydroxytyrosol biosynthesis is significantly improved by rearranging the metabolic flux among multiple pathways.

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