Nitrobenzene-degrading P. putida HS102 isolated by analog enrichment transformed 3-chloronitrobenzene(3CNB) into chloroaminophenol(CAP) by cometabolism. CAP, the degradation product of 3CNB by P. putida HS102, was further degraded by chlorobenzene-degrading Rhodococcus sp. HS501 carrying ortho-cleavage pathway, although degradation rate of CAP by Rhodococcus sp. HS501 was much slower than that of 3CNB by P. putida HS102. Both degradation steps required additional carbon and energy source. We obtained complete mineralization of 3CNB by mixed culture of P. putida HS102 and Rhodococcus sp. HS501 in the presence of succinate as a additional carbon source. P. putida HS102 in the mixed culture outgrew Rhodococcus sp. HS501 because its specific growth rate was much higher than that of Rhodococcus sp. HS501 on succinate. As the initial proportion of Rhodococcus sp. HS501 increased, the rate of cometabolic transformation of 3CNB by P. putida HS102 was enhanced. It seemed that some unidentified metabolites excreted by Rhodococcus sp. HS501 played an important role in the conversion of 3CNB to CAP by P. putida HS102. It was found that the degradability of 3CNB by mixed culture was strongly affected by additional carbon sources and the initial proportion of Rhodococcus sp. HS501.
