A series of lipophilic dodecyl hetaryl ketoximes (hetaryl = pyridin-2-yl, pyridazin-3-yl, pyrimidin-2-yl, pyrimidin-4-yl, pyrazin-2-yl as well as their methyl hetaryl homologues was synthesized and hydrolytic activity of their chelates with Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ in a micellar matrix of hexadecyltrimethylammonium bromide or in homogeneous aqueous solutions was investigated using 4-nitrophenyl acetate, 4-nitrophenyl hexanoate and 4-nitrophenyl diphenyl phosphate as model substrates. While Co 2+ and Cu 2+ chelates are almost inactive, those of Ni 2+ and Zn 2+ exhibit considerable activity. None of the studied chelates promotes hydrolysis of the used phosphate. The effective species are chelates of the metal : ligand stoichiometry 1 : 3 and 1 : 1 with Ni 2+ and Zn 2+ , respectively, when the ester cleavage proceeds in the micellar matrix. The 1 : 2 stoichiometry was found in aqueous solutions of Ni 2+ and Zn 2+ chelates of methyl ketoximes.Transition metal ions play an important role in many types of enzymes 1a,1b . Coordination to metal ions (most frequently Zn 2+ ) acidifies ionizable functions (e.g. covalently bound hydroxy group or coordinated water) in hydrolytic enzymes such as carboxypeptidase A 1a,1c , alkaline phosphatase 1a,1d and carbonic anhydrase 1a thus providing nucleophiles readily attacking electrophilic centres in substrates. A great number of simple models of hydrolytic metalloenzymes have been designed and studied over the years 2a-2d , many of them possessing hydrophobic moieties in their mole-

Biphenyl-utilizing polychlorinated biphenyls (PCB)-degrading bacteria were isolated from sites highly contaminated by PCBs, and their degradation abilities were determined using GC for typical commercial PCB mixtures (Delor 103 and Delor 106). Out of twelve strains which utilized biphenyl as a sole source of carbon and energy, strains Pseudomonas alcaligenes KP2 and P. fluorescens KP12, characterized by the BIOLOG identification system and the NEFERM test, were shown to significantly co-metabolize the PCB mixture Delor 103. DNA-DNA hybridization was used to compare both strains with well-known PCB-degraders Burkholderia cepacia strain LB400 and Ralstonia eutropha strain H850. The strain KP12 employs the same meta-fission route for degradation of chlorobenzoates as a chlorobiphenyl degrader Pseudomonas cepacia P166. Both isolates KP2 and KP12 belong to different phylogenetic groups, which indicates that the same geographical location does not ensure the same ancestor of degradative enzymes. We confirmed that also highly chlorinated and the most toxic congeners, which are contained in commercial PCB mixtures, can be biotransformed by members of indigenous bacterial-soil community under aerobic conditions.

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Aims: A possibility for the complementation of both ortho-and meta-cleavage pathway for chlorocatechols in one strain and its impact on degradation of chlorobenzoates accumulated during degradation of polychlorinated biphenyls was investigated. Methods and Results: Genes responsible for ortho-cleavage of chlorocatechols were subcloned into two biphenyl degraders and the activities of chlorocatechol dioxygenases responsible for ortho-and meta-cleavage in these hybrid strains were monitored spectrophotometrically and also electrochemically by ion-selective electrode. Conclusions: While strain Pseudomonas fluorescens S12/C apparently gained metabolic advantage from this gene manipulation, strain Burkholderia cepacia P166/C did not express better degradation features in comparison with the parental strain. Significance and Impact of the Study: This approach has the potential to enhance chlorocatechol metabolism in selected biphenyl degraders.