Survey of Microbial Diversity in Flood Areas during Thailand 2011 Flood Crisis Using High-Throughput Tagged Amplicon Pyrosequencing.

The Thailand flood crisis in 2011 was one of the largest recorded floods in modern history, causing enormous damage to the economy and ecological habitats of the country. In this study, bacterial and fungal diversity in sediments and waters collected from ten flood areas in Bangkok and its suburbs, covering residential and agricultural areas, were analyzed using high-throughput 454 pyrosequencing of 16S rRNA gene and internal transcribed spacer sequences. Analysis of microbial community showed differences in taxa distribution in water and sediment with variations in the diversity of saprophytic microbes and sulfate/nitrate reducers among sampling locations, suggesting differences in microbial activity in the habitats.

Reduction of uranium(VI) by soluble iron(II) conforms with thermodynamic predictions.

Soluble Fe(II) can reduce soluble U(VI) at rapid rates and in accordance with thermodynamic predictions. This was established by initially creating acidic aqueous solutions in which the sole oxidants were soluble U(VI) species and the sole reductants were soluble Fe(II) species. The pH of the solution was then increased by stepwise addition of OH(-), thereby increasing the potential for electron transfer from Fe(II) to U(VI).

Uranium reduction and resistance to reoxidation under iron-reducing and sulfate-reducing conditions.

Oxidation and mobilization of microbially-generated U(IV) is of great concern for in situ uranium bioremediation. This study investigated the reoxidation of uranium by oxygen and nitrate in a sulfate-reducing enrichment and an iron-reducing enrichment derived from sediment and groundwater from the Field Research Center in Oak Ridge, Tennessee. Both enrichments were capable of reducing U(VI) rapidly.

Can microbially-generated hydrogen sulfide account for the rates of U(VI) reduction by a sulfate-reducing bacterium?

In situ remediation of uranium contaminated soil and groundwater is attractive because a diverse range of microbial and abiotic processes reduce soluble and mobile U(VI) to sparingly soluble and immobile U(IV). Often these processes are linked. Sulfate-reducing bacteria (SRB), for example, enzymatically reduce U(VI) to U(IV), but they also produce hydrogen sulfide that can itself reduce U(VI).

Simple menaquinones reduce carbon tetrachloride and iron (III).

Cell-free supernatant from Shewanella oneidensis MR-1 reduced carbon tetrachloride to chloroform, a suspension of Fe(III) and solid Fe(III) to iron (II). The putative reducing agent was tentatively identified as menaquinone-1 (MQ-1)-a water-soluble menaquinone with a single isoprenoid residue in the side chain. Synthetic MQ-1 reduced carbon tetrachloride to chloroform and amorphous iron (III) hydroxide to iron (II).

Growth and cometabolic reduction kinetics of a uranium- and sulfate-reducing Desulfovibrio/Clostridia mixed culture: Temperature effects.

Bioremediation of contaminated soils and aquifers is subject to spatial and temporal temperature changes that can alter the kinetics of key microbial processes. This study quantifies temperature effects on the kinetics of an ethanol-fed sulfate-reducing mixed culture derived from a uranium-contaminated aquifer subject to seasonal temperature fluctuations. The mixed culture contains Desulfovibrio sp.