Growth of Dehalococcoides mccartyi strain CBDB1 by reductive dehalogenation of brominated benzenes to benzene

Brominated aromatics are used in many different applications but occur also naturally. Here, we demonstrate organohalide respiration and growth of Dehalococcoides mccartyi strain CBDB1 with 1,2,4-tribromobenzene, all three dibrominated benzene congeners and monobromobenzene. All bromobenzenes were fully dehalogenated to benzene. Growth yields were between 1.8 X 10(14) and 2.8 X 10(14) cells per mol of bromide released. Furthermore, a newly designed high-throughput methyl viologen-based photometric microtiter plate assay was established to determine the activity of the reductive dehalogenases in resting cell assays of strain CBDB1 with brominated aromatics as electron acceptors. Activities of 2.8-13.2 nkat per mg total cell protein (0.16-0.8 units per mg total cell protein) were calculated after cultivation of strain CBDB1 on 1,2,4-tribromobenzene. Mass spectrometric analyses and activity assays with whole cell extracts of strain CBDB1 gave strong evidence that four to six reductive dehalogenases were involved in the dehalogenation of all tested brominated benzenes, including the reductive dehalogenases CbdbA80 and CbrA.