Dataset for laboratory treatability experiment with activated carbon and bioamendments to enhance biodegradation of chlorinated ethenes

This dataset describes the outcome of a laboratory trichloroethene (TCE) treatability experiment with liquid activated carbon and bioamendments. The treatability experiment included unamended microcosms, bioamended microcosms with a Dehalococcoides containing culture and electron donor, and bioamended microcosms including liquid activated carbon (PlumeStop®). Data were collected frequently over an 85-day experimental period. Data were collected for the following parameters: redox sensitive species, chlorinated ethenes, non-chlorinated end-products, electron donors, compound specific isotopes, specific bacteria and functional genes. The reductive dechlorination of TCE could be described by a carbon isotope enrichment factor (εC) of -7.1 ‰. In the amended systems, the degradation rates for the TCE degradation were 0.08–0.13 d−1 and 0.05–0.09 d−1 determined by concentrations and isotope fractionation, respectively. Dechlorination of cis-DCE was limited. This dataset assisted in identifying the impact of different bioamendments and activated carbon on biodegradation of chlorinated ethenes. The dataset is useful in optimising design and setup for future laboratory and field investigations. This study provides novel information on the effect of low dose liquid activated carbon on chlorinated ethenes degradation by applying isotopic and microbial techniques, and by linking the outcome to a field case study. The data presented in this article are related to the research article “Assessment of chlorinated ethenes degradation after field scale injection of activated carbon and bioamendments: Application of isotopic and microbial analyses” (Ottosen et al., 2021)

Mechanism of Dihydrouridine Synthase 2 from Yeast and the Importance of Modifications for Efficient tRNA Reduction*

Dihydrouridine synthases (DUSs) are flavin-dependent enzymes that catalyze site-specific reduction of uracils in tRNAs. The mechanism of DUS 2 from Saccharomyces cerevisiae was studied. Previously published turnover rates for this DUS were very low. Our studies show that the catalytic cycle consists of reductive and oxidative half-reactions. The enzyme is reduced by NADPH rapidly but has a very slow oxidative half-reaction using in vitro transcribed tRNA substrates. Using tRNALeu purified from a DUS 2 knockout strain of yeast we obtained reaction rate enhancements of 600-fold over in vitro transcribed substrates, indicating that other RNA modifications are required for rapid uracil reduction. This demonstrates a previously unknown ordering of modifications and indicates that dihydrouridine formation is a later step in tRNA maturation. We also show that an active site cysteine is important for catalysis, likely in the protonation of uracil during tRNA reduction. Dihydrouridine of modified tRNA from Escherichia coli was also oxidized to uridine showing the reaction to be reversible