Anaerobic Biodegradation of organohalide pollutants: a crucial step towards the elucidation of proteins involved

Halogenated organic compounds (so-called organohalides) represent one of the major class of groundwater pollutants. The exploration of how organohalides are used as energy source is important in terms of ecosystem remediation but is also essential for the complete understanding of microbial metabolic interactions in the environment. Organohalide respiration (OHR) is a bacterial anaerobic process in which chlorinated compound, e.g. tetrachloroethene (PCE), is used as terminal electron acceptor. In the present work, Desulfitobacterium hafniense TCE1 and Dehalobacter restrictus, our model organohalide-respiring bacteria (OHRB) harbouring the pceABCT gene cluster, will be considered for the study of PCE respiration. To date, the function of PceA, the key catalytic enzyme in the process, and PceT, the dedicated molecular chaperone for PceA maturation, are well defined. However, the roles of PceB and PceC are not yet elucidated and the biochemistry of OHR electron transfer is still relatively elusive. Based on the genetic composition of the pce gene cluster, the hypothesis of a possible PceABC respiratory complex is tempting but the question remains largely unanswered. The present work represents an evaluation of the stoichiometry of PceA, PceB and PceC proteins via quantitative proteomics applied to the membranes fractions of our model organisms. In a second phase, the use of Blue-Native electrophoresis technology will be considered to investigate whether PceC participates in a membrane-bound protein complex together with PceA and PceB. The complementary results of both techniques will lead to identify the three proteins of interest in the membrane and is expected to shed light on the presence and composition of a PCE respiratory complex.