ISSN 0026-2617, Microbiology, 2010, Vol. 79, No. 3, pp. 321–326. © Pleiades Publishing, Ltd., 2010. Original Russian Text © O.N. Ponamoreva, T.Z. Esikova, Yu.A. Vlasova, B.P. Baskunov, V.A. Alferov, 2010, published in Mikrobiologiya, 2010, Vol. 79, No. 3, pp. 337–343. 321 Modern intensive industrial production leads to a considerable increase of environmental stress, which is evinced by significant contamination of the envi- ronment with toxic compounds. Among the most widespread pollutants in the contemporary world are a polymer based on 6-aminohexanoic acid and capro- lactam (polycaproamide) and polymer materials (caprone, nylon-6, nylon). Extensive application of polycaproamide in combination with its low bioavail- ability poses the problem of utilizing outworn caprone products. Hence, microbial biotransformation of polymers and caprolactam oligomers (6-aminohex- anoic acid oligomers) present in large amounts in the waste of polymer factories is quite an urgent matter. The linear caprolactam oligomers and nylon are utilized by microorganisms of the genera Achromo- bacter [1–3], Alcaligenes [4], Corynebacterium [5, 6], Flavobacterium [7], Pseudomonas [8], and Agromyces [9]. To date, the biochemistry of oligomer degradation has been studied best for Flavobacterium. Degradation of caprolactam oligomers requires the presence of sev- eral specific enzymes: 6-aminohexanoate-cyclic dimer hydrolase, 6-aminohexanoate dimer hydrolase, and endogenous 6-aminohexanoate oligomer hydro- lase; the genes encoding these enzymes are located on plasmids [10]. The cumulative activity of these three enzymes provides for transformation of the oligomer mixture to aminocapronoic acid. Thus, biodegradation of caprolactam oligomers begins with the hydrolysis of amide bonds by specific hydrolases with the formation of 6-aminohexanoate, which is then sequentially transformed by the enzymes of the caprolactam catabolic pathway into adipic semialdehyde, adipate, and Krebs cycle intermediates [11]. The capacity of bacterial strains from the genus Pseudomonas for growth on ε-caprolactam and its intermediates was shown to be controlled by conjuga- tive plasmids determining the degradation of ε-capro- lactam at least to succinate [12]. It should be noted that no data are available on the existence of any other catabolic pathways for caprolactam and its oligomers. It has been shown that bacteria may adapt to the presence of caprolactam oligomers, i.e., become able to biodegrade these xenobiotics. Several possible mechanisms of the onset of enzyme activities against synthetic substrates (including caprolactam oligo- mers) have been proposed: expansion of the substrate specificities of the enzymes present in a cell, activation of cryptic genes as a result of mutations, and alteration of regulatory mechanisms [5, 8]. The mechanisms of Transformation of Low-Molecular Linear Caprolactam Oligomers by the Caprolactam-Degrading Bacterium Pseudomonas putida BS394(pBS268) O. N. Ponamoreva a,1 , T. Z. Esikova b , Yu. A. Vlasova a , B. P. Baskunov b , and V. A. Alferov a a Tula State University, pr. Lenina 92, Tula, 300600 Russia b Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, Pushchino, Moscow oblast, 142290 Russia Received April 15, 2009 Abstract—A biosensor based on the most active caprolactam-degrading strain Pseudomonas putida BS394(pBS268) was used in the study of aerobic degradation of linear caprolactam oligomers by bacterial cells. The changes in the respiratory activity of the strain depend quantitatively on caprolactam dimer con- centration, making it possible to develop biosensors for detection of caprolactam oligomers in aqueous media. Based on mass spectrometry data, the scheme of transformation of linear caprolactam oligomers by the degrader strain P. putida BS394(pBS268) was proposed for the first time. It was found that oxidative tran- samination to respective dicarbonic acids may be one of the mechanisms of transformation of linear capro- lactam oligomers. According to the scheme proposed, the ability of the caprolactam-degrading strain to transform linear oligomers results from the broad substrate specificities of two enzymes of the caprolactam degradation pathway: 2-oxoglutarate-6-aminohexanoate transaminase and 6-oxohexanoate dehydrogenase. Transformation of linear oligomers is genetically controlled by the CAP biodegradation plasmid pBS268. Key words: biotransformation, linear caprolactam oligomers, CAP plasmid, transaminase activity, biosensors for caprolactam detection. DOI: 10.1134/S0026261710030070 EXPERIMENTAL ARTICLES 1 Corresponding author; e-mail: olga@tsu.tula.ru