Critical steps in degradation of chloroaromatics by rhodococci II. Whole‐cell turnover of different monochloroaromatic non‐growth substrates by Rhodococcus sp. An 117 and An 213 in the absence/presence of glucose

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Abstract
Kinetic experiments were performed to examine the effect of glucose and some related compounds on the removal of different monochloroaromatic non‐growth substrates (i.e. monochloroisomers of aniline, phenol and benzoate, respectively) by resting pre‐adapted cells of either Rhodococcus sp. An 117 or Rhodococcus sp. An 213. With both strains, the use of glucose as the additional carbon substrate allowed to differentiate between “cometabolizable” monochloroaromatics (i.e. 2‐chloroaniline, 3‐chloroaniline, 3‐chlorophenol, 4‐chlorophenol whose turnover appeared to be primarily limited by the availability of reducing power and/or energy to the cells) and those which were weakly removed “under any condition” due to narrow substrate specificity of the enzymes initiating the transformation process.In a second line of investigation, the reduction of ferricyanide by resting An 117 or An 213 cells was shown to exhibit a pattern of cosubstrate‐dependence analogous to that found for turnover of the “cometabolizable” monochloroaromatics. As demonstrated with different cell preparations of strain An 117, whole‐cell ferricyanide reduction strongly interferred with the cometabolic turnover of various monochloroaromatic non‐growth substrates. The results obtained are those to be expected if the former (NAD(P)H‐dependent) type of process, in preference to the second one, would consume the reducing equivalents which become available from the metabolism of glucose. They point out the opportunity to make use of the carbon substrate‐dependent whole‐cell reduction of ferricyanide (or of other external electron acceptors) as a rapid and inexpensive assay of pre‐screening for carbon compounds which would function as energy‐replenishing cosubstrates in the (cometabolic) turnover of xenobiotic non‐growth substrates by rhodococci.