A bacterial chloroform reductive dehalogenase: purification and biochemical characterization

© 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology. We report herein the purification of a chloroform (CF)-reducing enzyme, TmrA, from the membrane fraction of a strict anaerobe Dehalobacter sp. strain UNSWDHB to apparent homogeneity with an approximate 23-fold increase in relative purity compared to crude lysate. The membrane fraction obtained by ultracentrifugation was solubilized in Triton X-100 in the presence of glycerol, followed by purification by anion exchange chromatography. The molecular mass of the purified TmrA was determined to be 44.5 kDa by SDS-PAGE and MALDI-TOF/TOF. The purified dehalogenase reductively dechlorinated CF to dichloromethane in vitro with reduced methyl viologen as the electron donor at a specific activity of (1.27 ± 0.04) × 103units mg protein−1. The optimum temperature and pH for the activity were 45°C and 7.2, respectively. The UV-visible spectrometric analysis indicated the presence of a corrinoid and two [4Fe-4S] clusters, predicted from the amino acid sequence. This is the first report of the production, purification and biochemical characterization of a CF reductive dehalogenase

Organohalide respiring bacteria and reductive dehalogenases: Key tools in organohalide bioremediation

© 2016 Jugder, Ertan, Bohl, Lee, Marquis and Manefield.Organohalides are recalcitrant pollutants that have been responsible for substantial contamination of soils and groundwater. Organohalide-respiring bacteria (ORB) provide a potential solution to remediate contaminated sites, through their ability to use organohalides as terminal electron acceptors to yield energy for growth (i.e., organohalide respiration). Ideally, this process results in non- or lesser-halogenated compounds that are mostly less toxic to the environment or more easily degraded. At the heart of these processes are reductive dehalogenases (RDases), which are membrane bound enzymes coupled with other components that facilitate dehalogenation of organohalides to generate cellular energy. This review focuses on RDases, concentrating on those which have been purified (partially or wholly) and functionally characterized. Further, the paper reviews the major bacteria involved in organohalide breakdown and the evidence for microbial evolution of RDases. Finally, the capacity for using ORB in a bioremediation and bioaugmentation capacity are discussed

Genomic, transcriptomic and proteomic analyses of dehalobacter UNSWDHB in response to chloroform

Organohalide respiring bacteria (ORB) are capable of utilising organohalides as electron acceptors for the generation of cellular energy and consequently play an important role in the turnover of natural and anthropogenically-derived organohalides. In this study, the response of a Dehalobacter sp. strain UNSWDHB to the addition of trichloromethane (TCM) after a 50 h period of its absence (suffocation) was evaluated from a transcriptomic and proteomic perspective. The up-regulation of TCM reductive dehalogenase genes (tmrABC) and their gene products (TmrABC) was confirmed at both transcriptional and proteomic levels. Other findings include the upregulation of various hydrogenases (membrane-associated Ni-Fe hydrogenase complexes and soluble Fe-Fe hydrogenases), formate dehydrogenases, complex I and a pyrophosphate-energized proton pump. The elevated expression of enzymes associated with carbon metabolism, including complete Wood Ljungdahl pathway, during TCM respiration raises interesting questions on possible fates of intracellular formate and its potential role in the physiology of this bacterium. Overall, the findings presented here provide a broader view on the bioenergetics and general physiology of Dehalobacter UNSWDHB cells actively respiring with TCM

Corrigendum: Identification of cerebral metal ion imbalance in the brain of ageing octodon degus [Front. Aging Neurosci., 9, (2017) (66)] DOI: 10.3389/fnagi.2017.00066

Due to a misunderstanding, the O. degus brain specimen used in the study were obtained from the animal facility of the Pontificia Universidad Catholic University of Chile, not the animal facility of the University of Valparaiso as previously stated in the article. Therefore, in the animal methods section, the correct paragraph should read: Octodon degus were obtained from a breeding colony at the animal facility of the Pontifical Catholic University of Chile and maintained in a controlled temperature room (23 ± 1°C), under a 12:12 h light/dark cycle, with water and food provided ad libitum. At the time of this study, 16 male O. degus were grouped by age, from 12 to 36 months of age (n = 8 per group). Ages were selected to represent the development of AD-like pathology (36 months). All efforts were made to minimize animal discomfort and stress while also limiting the number of animals used. Aged animals were anesthetized with Equitesin (2.5 ml/kg, i.p.) and injected with heparin (4 USP/kg, i.p.). Afterward, brains were surgically removed from their skulls and frozen in isopentane at -78.5°C. All procedures were conducted according to animal protocols approved by the Institutional Animal Care and Use Committee at the Pontifical Catholic University of Chile