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The potential of 'Sphingobium indicum' (S.indicum) B90A for transforming [beta]- and [delta]- hexachlorocyclohexane (HCH) is reconfirmed. It is demonstrated that LinB is responsible for the transformation of [beta]-HCH to pentachlorocyclohexanol and tetrachlorocyclohexanediol in 'S. indicum' B90A and that LinB also acts on delta-HCH, analogously forming the respective pentachlorocyclohexanol and tetrachlorocyclohexanediol intermediates.

The enantioselective transformation of alpha-hexachlorocyclohexane (HCH) by LinA1 and LinA2 variants expressed as S-glutathione transferase (GST) fusion proteins in Escherichia coli BL21 is reported. Enantioselective degradation might be one of the key processes that determine enantiomer composition, especially when strains that contain only one of the linA genes, such as Sphingmonas paucimobilis UT26, prevail.

A novel bacterial strain that was capable of growing on the [beta]-tripeptide H-[beta]hVal-[beta]hAla-[beta]hLeu-OH as the sole carbon and nitrogen source was isolated from an enrichment culture. On the basis of physiological characterization, partial 16S rRNA sequencing, and fatty acid analysis, strain 3-2W4 was identified as a member of the family Sphingomonadaceae. Growth on the [beta]-tripeptide and the [beta]-dipeptide H-[beta]hAla-[beta]hLeu-OH was observed, and emerging metabolites were characterized. Small amounts of a persisting metabolite, the N-acetylated [beta]-dipeptide, were identified in both media. According to dissolved organic carbon measurements, 74 to 80% of the available carbon was dissimilated. The [beta]-peptide-degrading enzyme was purified from the crude cell extract of cells from strain 3-2W4 grown on complex medium. The enzyme was composed of two subunits, and the N-terminal sequences of both were determined. With this information, it was possible to identify the complete nucleotide sequence and to deduce the primary structure of the gene bapA. The gene encoded a [beta]-peptidyl aminopeptidase (BapA) of 402 amino acids that was synthesized as preprotein with a signal sequence of 29 amino acids. The enzyme was cleaved into two subunits (residues 30 to 278 and 279 to 402). It belonged to the N-terminal nucleophile (Ntn) hydrolase superfamily.

The isolation of an Sphingomonas xenophaga Bayram strain that efficiently degrades 4-(1-ethyl-1,4-dimethylpentyl)phenol is reported. The degradation experiments with five different 4-nonylphenol isomers have indicated that degradability is strongly dependent on the structure of the alkyl substituent.

The chlorobenzene dioxygenase from Pseudomonas sp. strain P51 converts substituted aromatic compounds to the S configuration at the carbon atom. The enantiomeric excess was higher than the same reaction catalyzed by toluene dioxygenases. This is of interest to the biotechnology industry because cis-dihydrodiols are building blocks for molecules with multiple chiral centers.

Two operons of the hbpCAD gene cluster are independently regulated and their expression is mediated by HbpR protein, which requires RNA polymerase-sigma(sup)54 and an integration host factor for complete activation. The transcriptional organization of the gene cluster facilitates orderly expression of the hbp genes and 2-hydroxybiphenyl degradation pathway.

Research has been conducted on the 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl degradationin Pseudomonas azelaica. The regulation of this degradation by the regulatory gene hbpR is discussed.

Pseudomonas sp. strain P51 cis-chlorobenzene dihydrodiol dehydrogenase (CDD)(TcbB) expressed in Escherichia coli DH5alpha (pTCB149) has been found to catalyze enantioselective dehydrogenase reactions. The study was carried out with the object of investigating the potential of CDD for enantiomeric resolution of chiral dihydrodiols. CDD preferentially oxidized the para-halogenated cis-toluene dihydrodiol enantiomers preferentially formed by chlorobenzene dioxygenase (CDO).

A study was conducted on whether Sphingomonas herbicidovorans initiates degradation of mecoprop by two alpha-ketoglutarate-dependent dioxygenase activities. The findings lend support to this hypothesis. Comparison of the conversion rates of different phenoxy herbicides showed that the two enzyme activities were distinct from that of TfdA, which catalyzes the first step in the degradation of 2,4-dichlorophenoxyacetic acid in Ralstonia eutropha JMP134.

Sphingomonas herbicidovorans MH utilizes the chiral herbicide mecoprop as a carbon and energy source, and completely degrades both R and S enantiomers of the herbicide in an enantioselective manner. The enantiomer-specific degradation pattern indicates that more than one enzyme system is involved in the degradation of the enantiomers. Stochiometric chloride release in growth experiments indicates degradation of the aromatic ring. The oxygen uptake rates by resting cell suspensions support the existence of enantioselective degradation.

The degradation of chiral 3-phenylbutyric acid by the gram-positive bacterium Rhodococcus rhodochorus PB1 was investigated. Only one enantiomer was used as a growth substrate. Data indicated that active cells were able to cometabolize the non-growth enantiomer to a dihydroxylated intermediate. Data also showed the importance of treating enantiomers separately in studies of chiral compound degradation.

Experimental analysis of Pseudomonas sp. strain HBP1 Prp reveals that Prp utilizes 2-isopropylphenol as its energy and carbon source and that it induces 2-isopropylphenol degradation through meta cleavage. Gas chromatography-mass spectrometry analysis reveals that 2-hydroxy-6-oxo-7-methylocta-2,4-dienoic acid and 3-isopropylcatechol are the respective products of the extradiol ring cleavage dioxygenase reaction and the initial monooxygenase reaction. The meta cleavage product hydrolyzes the dienoic acid to isobutyric acid.

Pseudomonas strain HBP1 cells cultured in a medium containing 2-hydroxy- or 2,2'-dihydroxybiphenyl was demonstrated to contain a functional monooxygenase activity dependent on NADH. Monooxygenase action on 2,2'-dihydroxybiphenyl yields 2,2',3-trihydroxybiphenyl which can also act as amonooxygenase substrate in a hydroxylation reaction that generates 2,2',3,3'-tetrahydroxybiphenyl. Catabolism of either 2,2',3-trihydroxybiphenyl or 2,2',3,3'-tetrahydroxybiphenyl is mediated via scission reactions. A characterization of the cleavage products is presented.

The confirmation of the metabolism and the pathway involved in the degradation of Pseudomonas sp. strain HBP1 Prp is discussed. Bacterial srains were chemically prepared and subjected to high-performance liquid chromatography, gas chromatography, gas chromatography-mass spectrometry UV-VIs spectroscopy and protein determination. High metabolite degradation activity was demonstrated.

Comamonas testosterone KF-1 has used 3-(4-sulfophenyl)butyrate (3-C4-SPC) with transient excretion of two degradation intermediates, whose identification has allowed to draft a complete degradative pathway for an sulfophenylcarboxylates (SPC). Biodegradation of the laundry surfactant linear alkylbenzenesulfonate (LAS) congeners are oxygenated and oxidized to about 50 SPC.

Study is conducted using O-labeling experiments to demonstrate that the ipso-hydroxy group is derived from molecular oxygen. The results shows that the alkyl cation derived from the alpha-quatermary nonylphenol 4-(1-ethyl-1,4-dimethyl-pentyl)-phenol through ipso-hydroxylation.

RdpA and SdpA were expressed and purified from Sphingomonas herbicidovorans MH as [His.sub.6]-tagged fusion proteins and the kinectic behavior of the enzymes with various substrates and cosubstrates were characterized. It was verified that RdpA and SdpA are two enantioselective alpha-ketoglutarate-dependent dioxygenases belonging to subgroup II by the measurement of enzyme activities with a novel coupled enzyme assay.

Studies done on the genetic background of phenoxyalkanoic acid degradation in Sphingomonas herbicidovorans strain MH are reported. Results suggest a different reservoir and reduced transfer for the genes of the modified ortho-cleavage pathway in Alphaproteobacteria compared with the ones in Beta and Gammaproteobacteria. The phenoxyalkanoic acid degradation pathway of strain MH is demonstrated to be unique in its composition, genetic organization and regulation.

Recently we showed that degradation of several nonylphenol isomers with α-quaternary carbon atoms is initiated by ipso-hydroxylation in Sphingobium xenophagum Bayram (F. L. P. Gabriel, A. Heidlberger, D. Rentsch, W. Giger, K. Guenther, and H.-P. E. Kohler, J. Biol. Chem. 280:15526-15533, 2005). Here, we demonstrate with 18O-labeling experiments that the ipso-hydroxy group was derived from molecular oxygen and that, in the major pathway for cleavage of the alkyl moiety, the resulting nonanol metabolite contained an oxygen atom originating from water and not from the ipso-hydroxy group, as was previously assumed. Our results clearly show that the alkyl cation derived from the α-quaternary nonylphenol 4-(1-ethyl-1,4-dimethylpentyl)-phenol through ipso-hydroxylation and subsequent dissociation of the 4-alkyl-4-hydroxy-cyciohexadienone intermediate preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the metabolism of certain α,α-dimethyl-substituted nonylphenols appears to also involve a reaction of the cation with the ipso-hydroxy group to form the corresponding 4-alkoxyphenois. Growth, oxygen uptake, and 18O-labeling experiments clearly indicate that strain Bayram metabolized 4-t-butoxyphenol by ipso-hydroxylation to a hemiketal followed by spontaneous dissociation to the corresponding alcohol and p-quinone. Hydroquinone effected high oxygen uptake in assays with induced resting cells as well as in assays with cell extracts. This further corroborates the role of hydroquinone as the ring cleavage intermediate during degradation of 4-nonylphenols and 4-alkoxyphenols. [ABSTRACT FROM AUTHOR]