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2-Chloro-4-methylphenoxyacetate is not a growth substrate for Alcaligenes eutrophus JMP 134 and JMP 134-1. It is, however, being transformed by enzymes of 2,4-dichlorophenoxyacetic acid metabolism to 2-chloro-4-methyl-cis,cis-muconate, which is converted by enzymatic 1,4-cycloisomerization to 4-carboxymethyl-2-chloro-4-methylmuconolactone as a dead end metabolite. Chemically, only 3,6-cycloisomerization occurs, giving rise to both diastereomers of 4-carboxychloromethyl-3-methylbut-2-en-4-olide. Those lactones harboring a chlorosubstituent on the 4-carboxymethyl side chain were surprisingly stable under physiological as well as acidic conditions.

During synthrophic growth of Hydrogenophaga palleronii (strain S1) and Agrobacterium radiobacter (strain S2) with 4-aminobenzene sulfonate (4ABS) only strain S1 desaminates 4ABS by regioselective 3,4-dioxygenation. The major part of the metabolite catechol-4-sulfonate (4CS) is excreted and further metabolized by strain S2. Although both organisms harbour activities of protocatechuate pathways assimilation of the structural analog 4CS requires first of all enzyme activities with broader substrate specificity: protocatechuate 3,4-dioxygenase and carboxymuconate cycloisomerase activities were identified which in addition to the natural substrates also convert 4CS and 3-sulfomuconate respectively. 4-Carboxymethyl-4-sulfobut-2-en-4-olide (4SL) was identified as a metabolite. Its further metabolism requires a desulfonating enzyme which eliminates sulfite from (4SL) and generates maleylacetate. Convergence with the 3-oxoadipate pathway is catalyzed by a maleyl acetate reductase, which was identified in cell-free extracts of both organisms S1 and S2. Characteristically, only strain S1 can oxidize sulfite and thus contributes to the interdependence of the two bacteria during growth with 4ABS.

The 1,3-dinitrobenzene-degrading Rhodococcus strain QT-1 was isolated under nitrogen limiting conditions from contaminated soil samples. Experimental data indicate tha 1,3-dinitrobenzene is metabolized via 4-nitrocatechol. Both compounds were oxidized by resting cells and nitro groups were completely eliminated as nitrite. Strain QT-1 utilizes both 1,3-dinitrobenzene and 4-nitrocatechol as source of nitrogen in the absence as well as in the presence of high amounts of ammonia. Growth on 4-nitrocatechol does not induce the enzyme(s) for the initial oxidation of 1,3-dinitrobenzene.

Two isoprene (2-methyl-1,3-butadiene) utilizing bacteria, Alcaligenes denitrificans ssp. xylosoxidans JE 75 and Rhodococcus erythropolis JE 77, were identified as highly efficient cooxidizers of TCE, cis- and trans-dichloroethene, 1,1-dichloroethene and vinyl-chloride. Isoprene grown cells eliminate chloride from TCE in stoichiometric amounts and tolerate high concentrations of TCE.

Pseudomonas sp. B13 was grown in continuous culture on 4-chlorophenol as the only carbon source. Maximum growth rate of 0.4 h(-1) was observed at a substrate concentration of greater than 0.01 mM and less than 0.15 mM. In addition to the enzymes of phenol catabolism, high specific 1,2-dioxygenase activities with chlorocatechols as substrates were found. The isomeric monochlorinated phenols were also totally degraded by 4-chlorophenol grown cells. (+)-2,5-Dihydro-4-methyl- and (+)-2,5-dihydro-2-methyl-5-oxo-furan-2-acetic acid were formed in high yield as dead-end catabolites from cooxidation of cresoles. Several dichlorophenols except 2,6-dichlorophenol were removed from the culture fluid by chlorophenol grown cells. Ring cleavage of chlorinated catechols were shown to be one of the critical steps in chlorophenol catabolism. A catabolic pathway for isomeric chlorophenols is discussed.

The hybrid strain Pseudomonas sp. WR4016 was subcultivated with increasing concentrations of 5-chlorosalicylate (5----10 mM) as sole carbon source over a period of 9 months. At intervals of approximately 3 months derivative strains WR4017, WR4018 and WR4019 were isolated which exhibited higher growth rates and increased substrate tolerance. Comparative analysis of the turnover rates of the key enzymes in chlorosalicylate degradation showed that the adaptation process did not result from structural modifications of these proteins. Instead, balanced overproduction of the salicylate hydroxylase and catechol 1,2-dioxygenase prevented the accumulation of toxic chlorocatechols and accounted for the reduction of the doubling times with 4- or 5-chlorosalicylate. A comparative analysis of a genetically engineered chlorosalicylate degrader PL300-1 showed similar regulatory patterns as the most advanced isolate WR4019 from the adaptation series.

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.

Methylsalicylate-grown cells of Pseudomonas sp. WR401 cometabolized 3-, 4- and 5-substituted halosalicylates to the corresponding halocatechols. Further degradation was unproductive due to the presence of high levels of catechol 2,3-dioxygenase. This strain acquired the ability to utilize 3-chlorobenzoate following acquisition of genes from Pseudomonas sp. B13 which are necessary for the assimilation of chlorocatechols. This derivative (WR4011) was unable to use 4- or 5-chlorosalicylates. Derivatives able to use these compounds were obtained by plating WR4011 on 5-chlorosalicylate minimal medium; one such derivative was designated WR4016. The acquisition of this property was accompanied by concomitant loss of the methylsalicylate phenotype. During growth on 4- or 5-chlorosalicylate the typical enzymes of chlorocatechol assimilation were detected in cell free extracts, whereas catechol 2,3-dioxygenase activity was not induced. Repeated subcultivation of WR4016 in the presence of 3-chlorosalicylate produced variants (WR4016-1) which grew on all three isomers.