Adenosine-5′-phosphosulfate (APS) as sulfate donor for assimilatory sulfate reduction in Rhodospirillum rubrum

Crude extracts of Rhodospirillum rubrum catalyzed the formation of acid-volatile radioactivity from (³⁵S) sulfate, (³⁵S) adenosine-5-phosphosulfate, and (³⁵S) 3-phosphoadenosine-5-phosphosulfate. An enzyme fraction similar to APS-sulfotransferases from plant sources was purified 228-fold from Rhodospirillum rubrum. It is suggested here that this enzyme is specific for adenosine-5-phosphosulfate, because the purified enzyme fraction metabolized adenosine-5-phosphosulfate, however, only at a rate of 1/10 of that with adenosine-5-phosphosulfate. Further, the reaction with 3-phosphoadenosine-5-phosphosulfate was inhibited with 3-phosphoadenosine-5-phosphate whereas this nucleotide had no effect on the reaction with adenosine-5-phosphosulfate. For this activity with adenosine-5-phosphosulfate the name APS-sulfotransferase is suggested. This APS-sulfotransferase needs thiols for activity; good rates were obtained with either dithioerythritol or reduced glutathione; other thiols like cysteine, 2-3-dimercaptopropanol or mercaptoethanol are less effective. The electron donor methylviologen did not catalyze this reaction. The pH-optimum was about 9.0; the apparent K _m for adenosine-5-phosphosulfate was determined to be 0.05 mM with this so far purified enzyme fraction. Enzyme activity was increased with K₂SO₄ and Na₂SO₄ and was inhibited by 5-AMP. These properties are similar to assimilatory APS-sulfotransferases from spinach and Chlorella.Abbreviations APS adenosine-5-phosphosulfate - PAPS 3-phosphoadenosine-5-phosphosulfate - 5-AMP adenosine-5-monophosphate - 3-AMP adenosine-3-monophosphate - 3-5-ADP 3-phosphoadenosine-5-phosphate (PAP) - DTE dithiorythritol - GSH reduced glutathione - BAL 2-3-dimercaptopropanol     

Observations on the reduction of non-activated carboxylates by Clostridium formicoaceticum with carbon monoxide or formate and the influence of various viologens

Crude extracts or supernatants of broken cells of Clostridium formicoaceticum reduce unbranched, branched, saturated and unsaturated carboxylates at the expense of carbon monoxide to the corresponding alcohols. The presence of viologens with redox potentials varying from E ₀=-295 to-650 mV decreased the rate of propionate reduction. The more the propionate reduction was diminished the more formate was formed from carbon monoxide. The lowest propionate reduction and highest formate formation was observed with methylviologen. The carbon-carbon double bond of E-2-methyl-butenoate was only hydrogenated when a viologen was present. Formate as electron donor led only in the presence of viologens to the formation of propanol from propionate. The reduction of propionate at the expense of a reduced viologen can be followed in cuvettes. With respect to propionate Michaelis Menten behavior was observed. Experiments are described which lead to the assumption that the carboxylates are reduced in a non-activated form. That would be new type of biological reduction.Non-standard abbreviations glc Gas liquid chromatography - HPLC high performance liquid chromatography - RP reverse phase; Mediators (the figures in parenthesis of the mediators are redox potentials E ₀ in mV) - CAV²⁺ carbamoylmethylviologen, 1,1-carbamoyl-4,4-dipyridinium dication (E ₀=-296 mV) - BV²⁺ benzylviologen, 1,1-dibenzyl-4,4-dipyridinium dication (E ₀=-360 mV) - MV methylviologen, 1,1-dimethyl-4,4-dipyridinium-dication (E ₀=-444 mV) - DMDQ²⁺ dimethyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-ethylendication (E ₀=-514 mV) - TMV²⁺ tetramethylviologen, 1,1,4,4-tetramethyl-4,4-dipyridinium dication (E ₀=-550 mV) - PDQ²⁺ propyldiquat, 2,2-dipyridino-1,1-propenyl dication (E ₀=-550 mV) - DMPDQ²⁺ dimethylpropyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-propenyl dication (E ₀=-656 mV) - PN productivity number=mmol product (obtained by the uptake of one pair of electrons) x (biocatalyst (dry weight) kg)^-1×h^-1     

Carotenoid pigments in a red strain of Rhizobium from Lotononis bainesii Baker

The carotenoid pigments of a Rhizobium strain isolated from Lotononis bainesii were found to be diglucosyl-4,4-diapocarotene-4,4-dioate and glucosyl-4,4-diapocarotene-4-oate-4-oic acid.5th publication in the series Carotenoids of Rhizobia [4th publication: Helv. chim. Acta 62: 2551–2557 (1979)]     

Catalysis of the peptide bond formation by 50 S subunits of E. Coli ribosomes with N-(formyl) methionine ester of adenylic acid as peptide donor

50 S subunits of E. coli ribosomes catalyze the reaction of the 2(3)-N-(formyl) methionine ester of adenosine 5-phosphate and Phe-tRNA resulting in peptide bond synthesis. Cytidine 5-phosphate stimulates this process on 50 S ribosomal subunits as well as on intact ribosomes. The obtained data show that the areas of the peptidyltransferase donor site which binds the 3-terminal fragment of peptidyl-tRNA possess completely formed structures on 50 S ribosomal subunits.     

Regioselective preparation of 2′, 3′-di-O-acylribonucleosides carrying lipophilic acyl groups through a lipase-catalysed alcoholysis

Candida antarctica B lipase-catalysed alcoholysis of 2, 3, 5-tri-O-hexanoyluridine (1a), 2, 3, 5-tri-O-dodecanoyluridine (1b), 2, 3, 5-tri-O-hexanoylinosine (1c) and 2, 3, 5-tri-O-dodecanoylinosine (1d) proceeded regioselectively to produce the corresponding 2, 3-di-O-acylribonucleosides 2a–d, providing a simple and efficient access to these new lipophilic compounds. Contrasting to the alcoholysis, enzymatic hydrolysis of 1a–d using different enzymes and experimental conditions did not proceed regioselectively.     

Presence of plastid and absence of mitochondrial DNA in male reproductive cells as evidence for cytoplasmic inheritance in Turnera ulmifolia and Zantedeschia aethiopica

Summary. Epifluorescence microscopy of mature pollen grains of Turnera ulmifolia and Zantedeschia aethiopica stained with 4,6-diamidino-2-phenylindole demonstrated the presence of fluorescent cytoplasmic DNA aggregates in the male reproductive cells of both species. Double staining of the cells with 4,6-diamidino-2-phenylindole and 3,3-dihexyloxacarbocyanine iodide in Technovit resin sections showed that the mitochondria of these cells did not correspond to the fluorescent cytoplasmic DNA aggregates. Electron microscopy studies revealed both plastids and mitochondria in the cells of these species. In addition, immunoelectron microscopy using an anti-DNA monoclonal antibody showed clear labeling of plastids but not mitochondria. These data provide cytological evidence for biparental plastid inheritance and maternal mitochondrial inheritance in these species.Correspondence and reprints: College of Life Sciences, Peking University, Beijing 100871, Peoples Republic of China.     

Transfer of germ plasm from the secondary to the primary gene pool in pennisetum

Summary Germ plasm from the A-genome of Pennisetum purpureum Schum. (AABB) of the secondary gene pool was transferred to cultivated pearl millet (AA) [P. glaucum (L.) R. Br.] by pollinating cytoplasmicnuclear male-sterile (cms) pearl millet with fertile allohexaploid pearl millet x P. purpureum hybrids (AAAABB). Certain allohexaploids used as pollinators on cms pearl millet resulted in 14-chromosome diploid pearl millet progenies. Three types of diploid pearl millet plants were produced in addition to the expected 28-chromosome AAAB-genome plants: (1) cms plants with only the A-genome, (2) cms plants with the A- and A-genomes, and (3) fertile plants with the A- and A-genomes. The latter group has allowed the utilization of genes for fertility restoration, stiff stalk, maturity, height, and morphological characteristics from the A-genome of P. purpureum in the pearl millet breeding program. Production of monoploid gametes by the allohexaploids appeared to be genetically controlled.     

Template-directed reactions of aminonucleosides

Summary We have studied the reactions between adenosine 5-phosphorimidazolide and 9-(2-amino-2-deoxyxylofuranosyl) adenine (I) or 3-methylamino-3-deoxyadenosine (II), both with and without a poly (U) template. We find that both amino compounds react much more rapidly than does adenosine, in the absence of a template. The rate of reaction is greatly enhanced by a poly (U) template in the case of I, but the enhancement is slight in the case of II.Abbreviations A adenosine - xylo A_NH2 9-(2-amino-2-deoxy--D-xylofuranosyl) adenine - A_NHMe 3-methylamino-3-deoxyadenosine - ImpA adenosine 5-phosphorimidazolide - A³ pA adenylyl-[35]-adenosine - A² pA adenylyl-[25]-adenosine - U_NPA adenylyl-[52]-2-amino-2-deoxyuridine - xylo A_NPA 9-[adenylyl-(52)-2-amino-2-deoxy--D-xylofuranosyl]adenine - A_(NMe)pA adenylyl-[53]-3-methylamino-3-deoxyadenosine - pA adenosine 5phosphate - AppA P₁, P₂-diadenosine 5pyrophosphate - (pA)_n n = 2, 3 [2-5]-linked oligomers of pA - A² pA² pA [2-5]-linked trinucleoside diphosphate of A - poly (U) polyuridylic acid     

Properties of a high-affinity cytokinin-binding protein from wheat germ

A soluble protein that interacts with a range of cytokinins was extensively purified from wheat (Triticum aestivum L.) germ. This protein has a K _d for kinetin of 2×10^-7 M. The binding of kinetin to the protein is inhibited by low concentrations of synthetic and naturally-occurring cytokinins including N⁶-benzyladenine, N⁶-benzyladenosine, kinetin riboside, N⁶-dimethylallyladenine, N⁶-dimethylallyladenosine, zeatin, zeatin riboside, N⁶-dimethyladenine and N⁶-dimethyladenosine. Adenine, adenosine and several non-N⁶-substituted adenine derivatives were ineffective as inhibitors of kinetin binding. While N⁶-butyryl-3,5-cyclic AMP, N⁶,2-O-dibutyryl-3,5-cyclic AMP and 2,3-cyclic AMP inhibited binding of kinetin to the protein, 3,5-cyclic AMP was ineffective. The kinetin-binding protein is heat-labile and pronase-sensitive. Kinetin-binding activity exactly co-chromatographs with a single peak of carbohydrate and protein on gel-filtration and is displaced from concanavalin A-Sepharose 4B by -methylglucoside. On gel filtration, the kinetin-binding protein behaves as a soluble protein with an apparent molecular weight of 180,000 daltons.     

In vitro investigation of α-amylase release from the digestive cells of the bivalve mollusc Pecten maximus: effect of second messengers and biogenic amines

The (neuro)endocrine control of enzyme release from invertebrate digestive cells remains poorly understood. A tissue dissociation procedure was developed to investigate the regulatory mechanisms of -amylase discharge from the cells of the stomach-digestive gland complex of the scallop Pecten maximus. The validity of the experimental system was tested by increasing the intracellular concentration of second messenger analogues (N ⁶,2-o-dibutyryl-adenosine-3,5 cyclic monophosphate and the ionophore A23187) known to mimic the activity of naturally occurring secretagogues in vertebrates: N ⁶,2-o-dibutyryl-adenosine-3,5 cyclic monophosphate increased the time and dose-dependent release of -amylase in a similar way as in vertebrates. A23187 was also very effective in inducing enzyme discharge. Since the in vitro bioassay was shown to be functional and because axon terminals were previously seen in close contact to -amylase secreting cells, the effect of some classic neurotransmitters was explored. Only the cholinergic agonist carbachol and dopamine evoked a secretory response. Maximal stimulation of -amylase release was reached at 10^-5 mol·l^-1 carbachol; at the same concentration dopamine was less effective than carbachol. By contrast, serotonin was totally inactive. The in vitro bioassay should prove useful for the identification of regulatory molecules involved in the control of enzyme discharge and to study stimulus secretion coupling mechanisms in scallop digestive cells.Abbreviations DBcAMP N ⁶, 2-O-dibutyryl-adenosine-3,5 cyclic monophosphate - cAMP adenosine-3,5 cyclic monophosphate     

Facile synthesis of 2′-substituted lactoses

Isopropylidenation of lactose with 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid gave two products, which were identified by¹H- and¹³C-NMR as 2,35,63,4-tri-O-isopropylidenelactose dimethyl acetal (1) and its 6-O-(2-methoxy)-isopropyl derivative (2). These products were used for the synthesis of 2-O-methyllactose (7), 2,6-di-O-methyllactose (9) and 2-O-benzyllactose (13).     

Polymerization of nucleotide analogues I: Reaction of nucleoside 5′-phosphorimidazolides with 2′-amino-2′-deoxyuridine

Summary 2-Amino-2-deoxyuridine reacts efficiently with nucleoside 5-phosphorimidazolides in aqueous solution. The dinucleoside monophosphate analogues were obtained in yields exceeding 80% under conditions in which little reaction occurs with the natural nucleosides.In a similar way, the 5-phosphorimidazolide of 2-amino-2-deoxyuridine undergoes self-condensation in aqueous solution to give a complex mixture of oligomers.The phosphoramidate bond in the dinucleoside monophosphate analogues is stable for several days at room temperature and pH 7. The mechanisms of their hydrolysis under acidic and alkaline conditions are described.Abbreviations A adenosine - C cytidine - G guanosine - U uridine - T thymidine - U_{N 3} 2-azido-2-deoxyuridine - U_{NH 2} 2-amino-2-deoxyuridine - ImpA adenosine 5-phosphorimidazolide - ImpU uridine 5-phosphorimidazolide - ImpU_{N 3} 2-azido-2-deoxyuridine 5-phosphorimidazolide - ImpU_{NH 2} 2-amino-2-deoxyuridine 5-phosphorimidazolide - pA adenosine 5-phosphate - pU uridine 5-phosphate - pU_{N 3} 2-azido-2-deoxyuridine 5-phosphate - pU_{NH 2} 2-amino-2-deoxyuridine 5-phosphate - UpA uridylyl-[35]-adenosine - UpU uridylyl-[35]-uridine - U_NpA adenylyl-[52]-2-amino-2-deoxy-uridine - U_NpU uridylyl-[52]-2-amino-2-deoxyuridine (pU_N)_n n=2,3,4 [25]-linked oligomers of pU_{NH 2} poly(A) polyadenylic acid - Im imidazole - MeIm l-methylimidazole     

Poly(U)-directed peptide-bond formation from the 2′(3′)-glycyl esters of adenosine derivatives

Summary The self-condensation of 2(3)-O-glycyl esters of adenosine, adenosine-5-(O-methylphosphate) and P₁, P₂-diadenosine-5-pyrophosphate in 6.2 mM solutions at pH 8.0 and -5°C in the presence of 12.5 mM poly(U) yields approximately 3 times as much diketopiperazine as reactions without poly(U). As the concentration of 2(3)-O-(glycyl)-P₁, P₂-diadenosine-5-pyrophosphate is decreased from 6.2 mM to 1.5 mM the yield of diketopiperazine in the presence of poly(U) decreases slightly from 6.6% to 5.2%, whereas, in the absence of poly(U) the yield of diketopiperazine decreases substantially from 2.4% to 0.75%. The enhanced yield of diketopiperazine that is attributed to the template action of poly(U) is temperature dependent and is observed only at temperatures below 10°C (5°C to -5°C) for 6.2 mM 2(3)-O-(glycyl)-adenosine-5-(O-methylphosphate) and below 23°C (15°C to -5°C) for 6.2 mM 2(3)-O-(glycyl)-P₁, P₂-diadenosine-5-pyrophosphate. The absence of a template effect at high temperatures is attributed to the melting of the organized helices. The hydrolysis half-lives at pH 8.0 and -5°C of 2(3)-O-(glycyl)-adenosine, 2(3)-O-(glycyl)-adenosine-5-(O-methylphosphate), 2(3)-O-(glycyl)-P₁, P₂-diadenosine-5-pyrophosphate, and 5-O-(glycyl)-adenosine in the presence of poly(U) are substantially larger than their half-lives in the absence of poly(U). The condensation of 2(3)-O-(glycyl)-adenosine yields 5% of 5-O-(glycyl)-adenosine in the presence of poly(U) compared to 0.7% in the absence of poly(U).Abbreviations DKP diketopiperazine - (gly)₂ glycylglycine - (gly)₃ glycylglycylglycine - AppA-gly 2(3)-O-(glycyl)-P₁, P₂-diadenosine-5-pyrophosphate - MepA-gly 2(3)-O-(glycyl)-adenosine-5-(O-methylphosphate) - Ado-2(3)-gly 2(3)-O-(glycyl)-adenosine - Ado-5-gly 5-O-(glycyl)-adenosine - Boc-gly N-tert-butyloxycarbonylglycine - AppA P₁, P₂-diadenosine-5-pyrophosphate - MepA adenosine-5-(O-methylphosphate) - AppA-Boc-gly 2(3)-O-(Boc-glycyl)-P₁, P₂-diadenosine-5-pyrophosphate - Ado-5-Boc-gly 5-O-(Boc-glycyl)-adenosine - Ado-2(3)-Boc-gly 2(3)-O-(Boc-glycyl)-adenosine     

Post-translational processing of 7S and 11S components of soybean storage proteins

The synthesis and processing of the major storage proteins in soybean cotyledons was studied both in vivo and in vitro. The and subunits of 7S as well as the 11S proteins are synthesized as higher molecular weight-precursors on membrane-bound polysomes. The initial translation products of the 7S are proteolytically cleaved during translation suggesting the removal of a signal peptide as evidenced by the presence of 2 and 2 peptides immunoreactive with 7S antibody in the in vitro chain completion products of the membrane-bound polysomes. This is followed or accompanied by cotranslational glycosylation, which increases their size equivalent to that of initially-synthesized precursors. In vivo pulse-labelled 7S and products are of slightly higher molecular weights than the immunoprecipitable chain-completion products, indicating further post-translational modifications. A slow post-translational processing during a period of 1.5 to 16 h yields the final 7S and glycoproteins.Acidic and basic subunits of the 11S protein appear to be synthesized from common large molecular weight (60K-59K) precursors. Antibodies to the 11S acidic component recognize both acidic and basic domains in the precursor while those raised against basic subunits appear to be specific for that region only. The processing of the 11S precursor is also very slow and occurs post-translationally. This slow rate of processing, coupled with a temporal difference in the synthesis of 7S and 11S components, suggests a highly coordinated mechanism for synthesis and packaging of these proteins into protein bodies during seed development.     

Geometry of the dry-state oligomerization of 2′,3′-cyclic phosphates

Summary Evaporation of a solution of thymidine plus either theexo or theendo diastereomer of uridine cyclic 2,3-O, O-phosphorothioate (U > p(S) in 1,2-diaminoethane hydrochloride buffer gave the 2,5 and 3,5 isomers of (P-thio) uridylylthymidine (Up(S)dT) in a ratio of 1:2 with a combined yield of about 20%. These isomers were re-converted to U > p(S) and dT by a reaction that is known to proceed by an in-line mechanism. Both the 2,5 and 3,5 isomers gave as product the same diastereomer of U > p(S) that had been used originally in their formation. These dry-state prebiotic reactions (Verlander, Lohrmann, and Orgel 1973) are thus shown to be stereospecific, and both the 2,5 and 3,5 internucleotide bonds are formed by an in-line mechanism.Abbreviations DAE 1,2-diaminoethane - HPLC high pressure liquid chromatography - RNase bovine pancreatic ribonuclease A, EC 3.1.4.22 - TEAB triethylammonium bicarbonate - tris tris(hydroxymethyl)aminomethane - UMP(S) uridine monophosphorothioate - U > p uridine cyclic 2,3-phosphate - U > p(S) uridine cyclic 2,3-O, O-phosphorothioate - Up(S)dT (P-thio)uridylylthymidine - U2p(R_p-S)5dT (P-thio)uridylylthymidine with theR configuration at phosphorous, and a 2,5 internucleotide linkage     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Evidence for a uridine-5′-diphosphate-glucose-protectedp-chloromercuribenzene sulfonic acid-binding site in sugarcane vacuoles

The uptake of uridine-5-diphosphate (UDP) glucose into vacuoles isolated fromSaccharum sp. cells was fully inhibited by pretreatment with 50 Mp-chloromercuribenzenesulfonic acid (PCMBS) and was not affected by N-ethylmaleimide up to a concentration of 5 mM. The addition of 10 mM UDP-glucose during the pretreatment partially protected the uptake mechanism from PCMBS inhibition, while the presence of adenosine-5-diphosphate (ADP) glucose or of various hexose-phosphates had no protective effect. Parallel experiments on the binding of [²⁰³Hg]PCMBS to the vacuoles showed that UDP-glucose and UDP added at 10 mM concentrations caused a 40% decrease in the binding of PCMBS while ADP-glucose did not inhibit the binding. The results indicate the presence in a previously proposed group translocator of at least one site that can bind UDP-glucose. This site, which is blocked by PCMBS, interacts with the nucleotide moiety of UDP-glucose.Abbreviations ADP-glucose adenosine-5-diphosphate glucose - PCMB p-chloromercuribenzoic acid - PCMBS p-chloromercuribenzenesulfonic acid - UDP uridine-5-diphosphate - UDP-glucose uridine-5-diphosphate glucose     

Biodegradation of seven polychlorinated biphenyls by a newly isolated aerobic bacterium (<Emphasis Type="Italic">Rhodococcus</Emphasis> sp. R04)

An aerobic bacterial strain, designated R04, belonging to the genus Rhodococcus has been isolated and characerized by 16S rDNA analysis. The capability of this strain to degrade seven different polychlorinated biphenyls (CBs), 500 ppm 3-CB, 3,4-CB, 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB in liquid medium, was evaluated. After 5 days of incubation, the concentration of chloride increased to 0.35 mM in cultures containing 3-CB and R04, whereas in cultures with 3,4-CB, 2,3,4,5-CB or 3,4,3,4-CB plus R04 the chloride content increased to 0.1 mM. However, non-stoichiometric amounts of chloride were produced in cultures with R04 and 4,4-CB, 2,4,6-CB and 2,4,5-CB. The spectrum of supernatants from R04 grown on seven PCBs had a UV-visible (UV-VIS) absorption at 200–500 nm, characteristic of biphenyl-derived cleavage products. Gas-chromatographic (GC) analysis showed that R04 was able to transform 100% of 3-CB and 3,4-CB after 1 day of incubation, and 95% of 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB after 5 days of incubation. The position of the chlorine substituents on the rings strongly influenced the degradation of polychlorinated biphenyls (PCBs) and their intermediate metabolites by Rhodococcus sp. R04. The degradation of PCBs was further evaluated by monitoring intermediate metabolites of PCBs.     

Oligomerization of deoxynucleoside-bisphosphate dimers: Template and linkage specificity

Evidence is presented that a poly(U) template selectively favors the oligomerization of the activated, 3–5 pyrophosphate-linked dimer pdAppdAp, in comparison with the 3–3 and 5–5 linked dimers. In the absence of poly(U), the 5–5linked dimer is the most reactive, and chains are formed which are more than 60 monomer units in length.Nucleic Acid-Like Structures V. For the previous paper in this series see Visscher and Schwartz (1988).     

A New Aerobic Gram-Positive Bacterium with a Unique Ability to Degrade ortho- and para-chlorinated Biphenyls

Strain B51 capable of degrading polychlorinated biphenyls (PCB) was isolated from soil contaminated with wastes from the chemical industry. Based on its morphological and chemotaxonomic characteristics, the strain was identified as a Microbacterium sp. Experiments with washed cells showed that strain B51 is able to degrade ortho- and para-substituted mono-, di-, and trichlorinated biphenyls (MCB, DCB, and TCB, respectively). Unlike the known PCB degraders, Microbacterium sp. B51 is able to oxidize the ortho-chlorinated ring of 2,2-DCB and 2,4-DCB and the para-chlorinated ring of 4.4-DCB. The degradation of 2,4-DCB and 4,4-DCB was associated with the accumulation of 4-chlorobenzoic acid (4-CBA) in the medium in amounts comprising 80–90% of the theoretical yield. The strain was able to utilize 2-MCB, 2,2-DCB, and their intermediate 2-CBA and to oxidize the mono(ortho)-chlorinated ring of 2,4,2-TCB and the di(ortho-para)-chlorinated ring of 2,4,4-TCB. A mixed culture of Microbacterium sp. B51 and the 4-CBA-degrading bacterium Arthrobacter sp. H5 was found to grow well on 1 g/l 2,4-DCB as the sole source of carbon and energy.