[Microbial degradation of mustard gas reaction masses: isolation and selection of degradative microorganisms, analysis of organic components of reaction masses and their biodegradation]

Bacterial strains growing in medium with mustard gas reaction masses (RM) as carbon sources were obtained. Growth cessation in the above medium was caused by the exhaustion of bioutilizable substrates, first of all monoethanolamine (MEA) and ethyleneglycol (EG), rather than by the accumulation of toxic metabolites in the culture liquid or in the cells. The main RM components, 1,4-perhydrothiazines (PHT), formed in the course of chemical detoxication of mustard gas, were identified and analyzed. The predominant component of PHT mixture was N-(2-hydroxyethyl)-2-methyl-1,4-perhydrothiazine hydrochloride. Concentrations of all the PHT decreased by 50% in the course of culture growth; their destruction was a result of microbial metabolism.

[Thiodiglycol metabolism in Alcaligenes xylosoxydans subsp. denitrificans]

The investigation of the degradation of thiodiglycol (the major product of mustard gas hydrolysis) by Alcaligenes xylosoxydans subsp. denitrificans strain TD2 showed that thiodiglycol is metabolized through the oxidation of its primary alcohol groups and the subsequent cleavage of C-S bonds in the intermediate products, thiodiglycolic and thioglycolic acids. The end products of these reactions are SO4(2-) ions and acetate, the latter being involved in the central metabolism of strain TD2. The oxidation of the sulfur atom gives rise to diglycolsulfoxide, which is recalcitrant to further microbial degradation. Based on the data obtained, a metabolic pathway of thiodiglycol transformation by A. xylosoxydans subsp. denitrificans strain TD2 is proposed.

[The bioutilization of thiodiglycol (a breakdown product of mustard gas): isolation of degraders and investigation of degradation conditions]

The Alcaligenes xylosoxydans subsp. denitrificans strain TD1 capable of degrading thiodiglycol (TDG), a breakdown product of mustard gas, was isolated from soil contaminated with breakdown products of this chemical warfare agent. The selected stable variant of TD1 (strain TD2) can grow on TDG with a lag phase of 4-8 h and a specific growth rate of 0.04-0.045 h-1. Optimal conditions for the biodegradation of TDG (pH, the concentration of TDG in the medium, and its relative content with respect to the bacterial biomass) were determined. TDG was found to be degraded with the formation of diglycolsulfoxide and thiodiglycolic acid. The data obtained can be used to develop approaches to the bioremediation of mustard gas-contaminated soils.

[Utilization of detoxification products of yperite-lewisite mixtures]

An approach to developing an ecologically safe technology for disposal of yperite-lewisite mixtures has been developed. The technology includes three sequential stages: (1) detoxification by alkaline hydrolysis (resulting in the loss of toxic properties); (2) electrochemical treatment of detoxification products (electrocoagulation, to eliminate arsenic salts, and electrochemical oxidation, to convert all organic components into bioutilizable matter); and (3) degradation of the compounds obtained at the two preceding stages by a bred microbial association.

[Scientific principles of complex ecologically-safe technology of mustard gas destruction]

The principles of complex, ecologically-safe technology for the destruction of battle gas mustard were worked out. This technology was based on the reaction alkaline detoxication of mustard; the major component of reaction mixture obtained after detoxication was thiodiglycol. Thorough thiodiglycol mineralization was achieved by electrochemical treatment. Electrolysis products were biologically utilized in biosorber.

[Oxidative dehalogenation of 2-chloro- and 2,4-dichlorobenzoates by Pseudomonas aeruginosa]

The strain Pseudomonas aeruginosa 142 isolated from the utilising PSBs bacterial association was capable of growth on 2-chloro- and 2,4-dichlorobenzoates as sole carbon sources, but it did not utilize 3-Cl, 4-Cl, 3,5-diCl- and 2,6-dichlorobenzoates. P. aeruginosa 142 dehalogenated 2-Cl-, 2,4-diCl- and 2,5-dichlorobenzoates in aerobic conditions. The release of chloride was not observed in microaerophilic and anaerobic conditions. The activities of catechol-1,2-dioxygenase and 4-chlorocatechol-1,2-dioxygenase were found in cell extracts after growth of this strain on 2,4-dichlorobenzoate. The presented results suggested that oxidative release of chloride in ortho-position is the first step of metabolism of 2-Cl-, 2,4-diCl- and 2,5-dichlorobenzoates. The further splitting of corresponding catechols is carried out by ortho-pathway.

[Plasmids for biodegradation of 2,6-dimethylpyridine, 2,4-dimethylpyridine, and pyridine in strains of Arthrobacter]

Arthrobacter crysallopoietes strain KM-4 degrading 2,6-dimethylpyridine and strain KM-4a degrading both 2,6-dimethylpyridine and pyridine, Arthrobacter sp. KM-4b degrading 2,4-dimethylpyridine were isolated from soil. Arthrobacter crystallopoietes KM-4 and Arthrobacter sp. KM-4b contain 100 Md plasmids pBS320 and pBS323. Arthrobacter crystallopietes KM-4a harbours a 100 Md and 80 Md plasmids. Plasmid curing and conjugation transfer results confirm that these plasmids are involved in degradation of 2,6-dimethylpyridine, 2,4-dimethylpyridine and pyridine. A mutant with lost ability to degrade 2,6-dimethylpyridine was isolated during the growth of strain KM-4 rifR at 42 degrees C. Electrophoretic analysis of the plasmid from temperature sensitive mutant revealed the deletion the size of 26 Md from pBS320 plasmid.

[Oxidation of dibenzofuran by Pseudomonas strains harboring plasmids of naphthalene degradation]

Pseudomonas strains harboring plasmids pBS3, pBS4, NAH7 were shown to carry out initial transformation of dibenzofurane to 4-[2'-(3'-hydroxy)-benzofuranyl]-2-keto-3-butenic acid due to broad substrate specificity of the enzymes of naphthalene catabolism nahA, nahB, nahC and nahD. These strains did not grow on dibenzofurane because of the inability of the enzyme nahE to split pyruvate of 4-[2'-(3' hydroxy)-benzofuranyl]-2-keto-3-butenic acid, which leads to accumulation of the latter. The strains harboring plasmids pBS2 and NPL-1 are not capable of any transformation of dibenzofurane.

[Plasmids for biphenyl, chlorobiphenyl and metatoluylate degradation from Pseudomonas putida]

Pseudomonas putida strain SU83, harbors the pBS311 plasmid coding for the degradation of biphenyl, 2- and 4-chlorbiphenyl, meta- and paratoluylate. The insertional mutants of the plasmid obtained by the transposon Tn5 insertion were isolated. One of the mutants was used for cloning of the biphenyl degradation genes. The plasmid pBS311:: Tn5 DNA was inserted into the BamHI site of the plasmid pBR322 and cloned. 11 recombinants of 354 tested were treated with 0.1% solution of 2,3-dioxybiphenyl. One of them has acquired the yellow colour testifying to conversion of 2,3-dioxyphenyl to "2-hydroxy-6-keto-6-phenylhexa-2,4-diene acid. The recombinant plasmid pBS312 from this clone is 10.5 kb in size, the size of the insert being 6.2 kb. Escherichia coli SU185 cells harbouring pBS312 are able to support metacleavage of 2,3-dioxybiphenyl, 3-methylcatechol and catechol, but not of 4-methylcatechol. The results suggest the cloned fragment to contain a gene for 2,3-dioxybiphenyl-1,2-dioxygenase, the third enzyme for biphenyl catabolism.

[Purification and properties of two enzymes of meta-cleaving the aromatic ring controlled by the biphenyl biodegradation plasmid pBS 241 from Pseudomonas putida]

It was shown that two metapyrocatechases (EC 1.13.11.2) function in Pseudomonas putida BS893. Biphenyl degradative plasmid pBS241 carries the genes of these enzymes. The basic properties of the both enzymes, i. e., MPC1 and MPC2, were investigated. It was found that MPC1 is an enzyme with a molecular mass of 135 kD and has a heterotetrameric subunit structure (alpha 2 beta 2), being made up of two non-identical polypeptides with Mr of 34 and 22.5 kD; pI is 5.15, the pH optimum is at 8.0, a temperature optimum is at 54 degrees C. MPC2 has a molecular mass of 154 kD and possesses a homotetrameric subunit structure (alpha 4); it consists of identical polypeptides with Mr of 41 kD and has a pI of 4.95, a pH optimum at 7.5 and a temperature optimum at 60 degrees C. The substrate specificity of the enzymes was studied, and the Km and Vmax values for substituted catechols were determined. MPC1 shows a high affinity for 2.3-dihydroxybiphenyl and hydrolyzes 3-methylcatechol and catechol (but not 4-methylcatechol) at a low rate. MPC2 has a moderate affinity for catechol, 3- and 4-methylcatechols, but is incapable of cleaving 2.3-dihydroxybiphenyl. Both enzymes share in common some typical properties of metapyrocatechases. The different role of MPC1 and MPC2 in biphenyl catabolism is discussed.

[Catabolism of biphenyl by Pseudomonas putida BS 893 strain containing the biodegradation plasmid pBS241]

The isolation and identification of biphenyl catabolism products in Pseudomonas putida BS 893 (pBS241) showed the presence of benzoic, m-hydroxybenzoic and cinnamic acids. The two latter compounds were not found in biphenyl degradation by other bacterial strains. P. putida BS 893 (pBS241) differed from other biphenyl-positive Pseudomonas strains in the enzyme activity. These differences may stem from peculiarities in the pathway of biphenyl catabolism controlled by plasmid pBS241.

[Regulation of the synthesis of the key enzymes for naphthalene catabolism in Pseudomonas putida and Pseudomonas fluorescens carrying the biodegradation plasmids NAH, pBS3, pBS2 and NPL-1]

Regulation of the synthesis of key enzymes catalysing naphthalene catabolism was studied in Pseudomonas strains containing different plasmids of naphthalene biodegradation. The synthesis of naphthalene oxygenase, salicylate hydroxylase, catechol-1,2-oxygenase and cathechol-2,3-oxygenase was shown to be regulated in both the coordinated and non-coordinated manner.

[Naphthalene oxidation by a Pseudomonas putida strain carrying a mutant plasmid]

Naphthalene oxidation by a parent and a mutant strain of Pseudomonas putida was studied. The parent strain contained a plasmid NPL-1 which controlled oxidation of naphthalene to salicylic acid and was capable of oxidizing salicylate. The mutant strain did not oxidize salicylate because of a mutation in salicylate hydroxylase; it contained also a mutant plasmid NPL-41 which determined constitutive synthesis of naphthalene oxygenase. Salicylic acid which accumulated as a product of naphthalene catabolism in the cultural broth of the wild strain was found to undergo further oxidation by the population of growing cells. The content of salicylic acid in the cultural broth of the mutant strain reached maximum and then remained constant. An anion-exchange resin was tested in order to prevent the inhibition of naphthalene oxygenase by salicylate and to increase the yield of salicylic acid. The transmissible character of the mutant plasmid NPL-41 makes it possible, with the aid of conjugation, to construct Pseudomonas strains which would oxidize naphthalene to salicylic acid without further degradation of this compound.

[Study of the initial reaction of enzymatic oxidation of 1,8-dimethylnaphthalene]

Crude enzymatic preparation has been obtained from Pseudomonas bacteria which oxidises 1,8-DMN during 10-hour incubation with the following formation of the same products which are formed when this compound is oxidized by the intact cells. The first product of the oxidation is 1-methyl-8-oxymethylnaphtalene (compound I), obtained as a result of hydroxylation of one methyl group. Probably hydroxylase of 1,8-DMN may be referred to the class of oxigenases of the basis of the absence of 18O incorporation from H218O to compound I, and also resulting from the data on absorption of molecular oxygen during the reaction. The enzyme is completely inhibited by chelating agents of Fe2+ NAD(P)H and Fe2+ stimulates the reaction of 1.8 DMN oxidation.