GENERATION OF A TRANSIENT NON-CULTURABLE STATE IN PSEUDOMONAS-PUTIDA DURING DETOXIFICATION OF N-ETHYLMALEIMIDE

The response of Pseudomonas putida to the electrophile N-ethylmaleimid e (NEM) has been investigated. Treatment with low levels of NEM (20-30 mu M) led to transient growth inhibition followed by recovery of norm al growth. Stationary phase cells acquired resistance to NEM; one comp onent of this tolerance was a more rapid metabolism of NEM. In exponen tial phase cells, the period of growth inhibition was associated with detoxification of NEM. Detoxification was biphasic and cells lost the ability to form colonies on minimal agar plates during the first phase of detoxification. Full viability was retained on MacConkey agar. Pep tones are the active components in MacConkey medium. Addition of pepto nes to minimal agar restored colony-forming ability, but each peptone source had a different efficiency. These data suggest that a deficienc y in the ability to assimilate nitrogen is a consequence of NEM treatm ent.