Isolation and partial characterisation of dehalogenase-deficient mutants of aRhizobiumsp.

A fast-growing species of Rhizobium that can utilise 2,2-dichloropropionate and 2-chloropropionate as sole sources of carbon and energy was mutated to give strains which had lost this ability. Such mutants lacked two inducible dehalogenase activities that were present in the parent organism. Secondary mutants which had regained the ability to grow on 2,2-dichloropropionate (2,2DCP) and/or 2-chloropropionate (2CP) were isolated from the original mutants. Some were constitutive for dehalogenase I and did not form dehalogenase II, some were constitutive for dehalogenase II and did not form dehalogenase I, whilst others, like the parent organism, formed both dehalogenases inducibly. A possible model for the control of dehalogenase synthesis is proposed.