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1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) is the peri-chlorinated derivative of 1,1-diphenylethylene (DPE). Biodegradation of DDE and DPE by bacteria has so far not been shown. Pure cultures of aerobic bacteria involved in biodegradation of styrene and polychlorinated biphenyls (PCB) were therefore screened for their ability to degrade or cometabolize DPE and DDE. Styrene-metabolizing bacteria (Rho-dococcus strains S5 and VLB150) grew with DPE as their sole source of carbon and energy. Polychlorinated-biphenyl-degrading bacteria (Pseudomonas fluorescens and Rhodococcus globerulus) were unable to degrade DPE even in the presence of an easily utilizable cosubstrate, biphenyl. This is the first report of the utilization of DPE as sole carbon and energy source by bacteria. All the tested bacteria failed to degrade DDE when it was provided as the sole carbon source or in the presence of the respective degradable cosubstrates. DPE transformation could also be detected in cell-free extracts of Rhodococcus S5 and VLB150, but DDE was not transformed, indicating that cell wall and membrane diffusion barriers were not limiting biodegradation. The results of the present study show that, at least for some bacteria, the chlorination of DDE is the main reason for its resistance to biodegradation by styrene and DPE-degrading bacteria.

The TOL plasmid-encoded enzymes of the methylbenzoate pathway in Pseudomonas putida mt-2 cometabolized 3-trifluoromethyl (TFM)-benzoate. Two products, 3-TFM-1,2-dihydroxy-2-hydrobenzoate (3-TFM-DHB) and 2-hydroxy-6-oxo-7,7,7-trifluoro-hepta-2,4-dienoate (7-TFHOD) were identified chemically and by spectroscopic properties. TFM-substituted analogues of the metabolites of the methylbenzoate pathway were generally converted at drastically reduced rates. The catechol-2,3-dioxygenase from Pseudomonas putida showed moderate turnover rates with 3-TFM-catechol. The catechol-1,2-dioxygenase of Rhodococcus rubropertinctus N657 was totally inhibited by 3-TFM-catechol and did not cleave this substrate. Hammett-type analysis showed the catechol-1,2-dioxygenase reaction to be strongly dependent on the electronic nature of the substituents. Electronegative substituents strongly inhibited catechol cleavage. The catechol-2,3-dioxygenase reaction, however, was only moderately sensitive to electronegative substituents.

The novel enzyme 4-methyl-2-enelactone methyl-isomerase was detected in, and purified to electrophoretic homogeneity from, p-toluate-grown cells of Rhodococcus rhodocrous N75, a nocardioform actinomycete. The enzyme was very thermostable and had a native Mr of 75,500; as the monomer had an Mr of 17,000, the enzyme is probably tetrameric. The new isomerase is highly specific with respect to its lactone substrate, only accepting (+)-(4S)-4-methylmuconolactone (4-carboxymethyl-4-methylbut-2-en-1,4-olide), and the putative isomerization reaction intermediate 1-methylbislactone ((-)-1-methyl-3,7-dioxo-2,6-dioxabicyclo-[3.3.0]octane) as substrates, and yielding (-)-(4S)-3-methylmuconolactone (4-carboxymethyl-3-methylbut-2-en-1,4-olide) as product. Some other lactone analogues acted as competitive inhibitors. Our data suggest that the isomerization does not involve actual methyl migration, but proceeds via the 1-methybislactone.