SEARCH · PubMed Health

Results for “Rhodococcus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,585 records · Page 88Linked to original sources

PubMedDate not supplied

Enantioselective biotransformations using rhodococci.

The use of enzymes and whole cells in enantioselective biotransformation reactions is briefly reviewed. A Rhodococcus strain is shown to possess nitrile hydratase and amidase activity. The organism can be used for the enantioselective biotransformation of racemic alpha-amino amides to (S) alpha-amino acids with an enantiomeric excess (ee) of > 98%. Enantioselectivity is effectively time independent allowing easy quantitative conversion of racemic mixtures into enantiomerically pure alpha-amino amides and alpha-amino acids. The reaction is effective for a wide range of alpha-substituents. The pH-dependence of the reaction indicates that the alpha-amino amide is bound to the amidase enzyme in its neutral unprotonated form.

Amides↗

PubMedDate not supplied

Application of whole cell rhodococcal biocatalysts in acrylic polymer manufacture.

Rhodococci are ubiquitous in nature and their ability to metabolise a wide range of chemicals, many of which are toxic, has given rise to an increasing number of studies into their diverse use as biocatalysts. Indeed rhodococci have been shown to be especially good at degrading aromatic and aliphatic nitriles and amides and thus they are very useful for waste clean up where these toxic chemicals are present. The use of biocatalysts in the chemical industry has in the main been for the manufacture of high-value fine chemicals, such as pharmaceutical intermediates, though investigations into the use of nitrile hydratase, amidase and nitrilase to convert acrylonitrile into the higher value products acrylamide and acrylic acid have been carried out for a number of years. Acrylamide and acrylic acid are manufactured by chemical processes in vast tonnages annually and they are used to produce polymers for applications such as superabsorbents, dispersants and flocculants. Rhodococci are chosen for use as biocatalysts on an industrial scale for the production of acrylamide and acrylic acid due to their ease of growth to high biomass yields, high specific enzyme activities obtainable, their EFB class 1 status and robustness of the whole cells within chemical reaction systems. Several isolates belonging to the genus Rhodococcus have been shown in our studies to be among the best candidates for acrylic acid preparation from acrylonitrile due to their stability and tolerance to high concentrations of this reactive and disruptive substrate. A critical part of the selection procedure for the best candidates during the screening programme was high purity product with very low residual substrate concentrations, even in the presence of high product concentrations. Additionally the nitrile and amide substrate scavenging ability which enables rhodococci to survive very successfully in the environment leads to the formation of biocatalysts which are suitable for the removal of low concentrations of acrylonitrile and acrylamide in waste streams and for the removal of impurities in manufacturing processes.

Acrylic Resins↗

PubMedDate not supplied

Cloning of genes that have environmental and clinical importance from rhodococci and related bacteria.

Generalised and specialised transduction systems were developed for Rhodococcus by means of bacteriophage Q4. The latter was used in conjunction with DNA from an unstable genetic element of R. rhodochrous to construct resistance plasmids which replicate in strains of R. equi, R. erythropolis and R. rhodochrous. One of the plasmids, pDA21, was joined with Erythropolis coli suicide vector pEcoR251 to obtain shuttle plasmids maintained in both rhodococci and E. coli. Conjugation between these rhodococcal strains demonstrated all were interfertile with each other and that some of the determinants for this were located on the unstable genetic element. Plasmids derived from this element, such as pDA21, carried the conjugative and self-incompatibility capacities; deletion analysis revealed that DNA necessary for self-incompatibility overlapped with that for arsenic resistance. Rifampicin is one of the principal chemotherapeutic agents used to treat infections by rhodococci and related organisms. The genes responsible for two types of inactivation have been cloned. The sequence of the R. equi DNA responsible for decomposition of the antibiotic strongly resembled those of monooxygenases acting upon phenolic compounds, consistent with the presence of a naphthalenyl moiety in the rifampicin molecule. Antibiotic resistance conferred by the gene was surprisingly specific to the semisynthetic compounds rifampicin (150-fold increase) and rifapentine (70-fold). Similar specificity was observed with the other inactivation gene cloned, which ribosylates rifampicin at the 23-hydroxyl position. A 60-bp sequence upstream of the monooxygenase and ribosylation genes is strikingly similar suggesting a shared pattern of regulation. Rhodococcal arsenic resistance and azo dye degradation genes have been cloned and characterised.

Actinomycetales↗

PubMedDate not supplied

Rhodococcal systematics: problems and developments.

Various approaches that have been used in the development of a system of classification for the genus Rhodococcus are discussed. The application of chemotaxonomic, molecular systematic and numerical phenetic methods have greatly contributed to improvements in the systematics of rhodococci and related mycolic-acid containing actinomycetes. The genus currently encompasses twelve validly described species but improved diagnostic methods are needed to distinguish between them. In addition, evidence from 16S ribosomal RNA sequencing suggests that the genus is still heterogeneous.

Bacterial Typing Techniques↗

PubMed2000

Purification, characterization and crystallization of enzymes for dibenzothiophene desulfurization.

DszC and DszA, DBT monooxygenase and DBT sulfone monooxygenase, respectively, involved in dibenzothiophene (DBT) desulfurization, were purified to homogeneity from Rhodococcus erythropolis D-1. The two enzymes were crystallized and enzymologically characterized. We found a high activity of flavin reductase in the non-DBT-desulfurizing bacterium, Paenibacillus polymyxa A-1, which is essential for DszC and A activities, and purified to homogeneity and characterized the enzyme.

Biodegradation, Environmental↗

PubMed1999

Biodegradation of a high molecular weight aliphatic ether--indications of an unusual biodegradation pathway.

An aliphatic ether (1-phytanyl-1-octadecanyl-ether) of high molecular weight was used as a sole carbon source in degradation experiments with different aerobic bacteria. The enriched culture B5, obtained from fuel contaminated soils, was able to degrade the substance for more than 90%. A culture of Rhodococcus ruber was similarly effective. Detailed investigation of the metabolites allowed us to characterize an unusual degradation pathway via a mid-chain oxidation mechanism ('internal oxidative pathway'). Obviously, formation of intermediate alkenes mainly at the unbranched side chain was a prerequisite for bacterial degradation of the added substrate. Degradation proceeded - in spite of the usually preferred terminal oxidation - via oxidation of the internal double bond and was followed by an ester cleavage. In turn, a series of alcohols was formed which were subsequently oxidized to the respective carboxylic acids and were further metabolized via the normal beta-oxidation pathway.

Alcohols↗

PubMed2003

Cloning of a rhodococcal promoter using a transposon for dibenzothiophene biodesulfurization.

The expression of biodesulfurization genes (dsz) in Rhodococcus erythropolis strain KA2-5-1 is repressed by sulfate which is the product of biodesulfurization. The application of a sulfate non-repressible promoter could be effective in enhancing biodesulfurization. A promoter-probe transposon was constructed using the promoterless, red-shifted green fluorescence protein gene (rsgfp). A 340 bp putative promoter element, designated kap1, was isolated from a strain KA2-5-1 recombinant that had shown high fluorescence intensity. The activity of kap1 was not affected by 1 mM sulfate. It gave about a 2-fold greater activity than the 16S ribosomal RNA promoter in R. erythropolis strain KA2-5-1 and is therefore useful for expressing desulfurization genes in rhodococcal strains.

Biodegradation, Environmental↗

PubMed2003

Residue 345 of dibenzothiophene (DBT) sulfone monooxygenase is involved in C-S bond cleavage specificity of alkylated DBT sulfones.

Rhodococcus erythropolis IGTS8 that possesses dibenzothiophene sulfone monooxygenase mutated at residue 345 (Q345A), can degrade octyl sulfide on which the wild strain cannot grow. Residue 345 and the neighbouring residues were changed by site-directed mutagenesis. Only DszA changed at residue 345 gave an altered C-S bond cleavage pattern of 3-methyl DBT sulfone. This residue is therefore involved in C-S bond cleavage specifically for alkylated DBT sulfone.

Amino Acid Sequence↗

PubMed2000

Resident aerobic microbiota of the adult human nasal cavity.

Recent evidence strongly suggests that the microbiota of the nasal cavity plays a crucial role in determining the reaction patterns of the mucosal and systemic immune system. However, little is known about the normal microbiota of the nasal cavity. The purpose of this study was to determine the microbiota in different parts of the nasal cavity and to develop and evaluate methods for this purpose. Samples were collected from 10 healthy adults by nasal washes and by swabbing of the mucosa through a sterile introduction device. Both methods gave results that were quantitatively and qualitatively reproducible, and revealed significant differences in the density of the nasal microbiota between individuals. The study revealed absence of gram-negative bacteria that are regular members of the commensal microbiota of the pharynx. Likewise, viridans type streptococci were sparsely represented. The nasal microbiota was dominated by species of the genera Corynebacterium, Aureobacterium, Rhodococcus, and Staphylococcus, including S. epidermis, S. capitis, S. hominis, S. haemolyticus, S. lugdunensis and S. warneri. These studies show that the microbiota of the nasal cavity of adults is strikingly different from that of the pharynx, and that the nasal cavity is a primary habitat for several species of diphtheroids recognized as opportunistic pathogens. Under special circumstances, single species, including IgA1 protease-producing bacteria, may become predominant in a restricted area of the nasal mucosa.

Actinomycetales↗

PubMed2003

Nitrile biotransformations for the synthesis of enantiomerically enriched Baylis-Hillman adducts.

Catalysed by the nitrile hydratase/amidase-containing Rhodococcus sp. AJ270 cells, a number of beta-aryl- and beta-alkyl- beta-hydroxy-alpha-methylenepropiononitriles (the Baylis-Hillman nitriles) 1 underwent hydrolysis under mild conditions to produce the corresponding enantiomerically enriched Baylis-Hillman amides 2 and acids 3. The enantioselectivity of the biotransformations was strongly determined by the steric effect of the substituents at the beta-position of the substrates. The protection of the free hydroxy of beta-phenyl-beta-hydroxy-alpha-methylenepropiononitrile 1a by methylation led to the enhancement of enantiocontrol of the biohydrolysis.

Amides↗

PubMed2006

Biocatalytic deuterium- and hydrogen-transfer using over-expressed ADH-'A': enhanced stereoselectivity and 2H-labeled chiral alcohols.

Employing the over-expressed highly organic solvent tolerant alcohol dehydrogenase ADH-'A' from Rhodococcus ruber DSM 44541, versatile building blocks, which were not accessible by the wild type catalyst, were obtained in > 99% e.e.; furthermore, employing d8-2-propanol as deuterium source, stereoselective biocatalytic deuterium transfer was made feasible to furnish enantiopure deuterium labeled sec-alcohols on a preparative scale employing a single enzyme.

Alcohol Dehydrogenase↗

PubMed2003

A rapid and sensitive fluorometric assay method for the determination of nitrilase activity.

A rapid, simple and sensitive fluorometric assay method for the determination of nitrilase activity is described. 3-Cyanopyridine was hydrolysed to nicotinic acid by Rhodococcus rhodochrous and the liberated NH(3) was allowed to react with buffered o -phthaldialdehyde-2-mercaptoethanol solution (pH 7.4) to form a fluorochrome. The fluorescence intensity was found to be stable after 20 min incubation at room temperature, and the optimum pH for the reaction was found to be 7.4. The fluorescence intensity was linearly related to enzyme activity with the substrate concentration ranging from 100 to 1000 mM. The activity determined by the proposed method correlates ( r =0.9625) well with the established Berthelot method. The proposed method is more sensitive than the existing methods for the determination of nitrilase activity.

Aminohydrolases↗

PubMed2006

Enzymatic C-4 deacetylation of 10-deacetylbaccatin III.

Second-generation paclitaxel analogues that require replacement of the C-4 acetate by other substituents are in development. An enzyme able to specifically remove the C-4 acetate from paclitaxel could simplify preparation of the analogues. Several strains were isolated from soil samples that contain enzyme activities able to 4-deacetylate 10-DAB (10-deacetylbaccatin III). Selection was made using plates containing 10-DAB as the sole carbon source and screening colonies for deacetylation of 10-DAB. Two strains initially isolated were identified as Rhodococcus sp. and deposited with the A.T.C.C. (Manassas, VA, U.S.A.) as strains 202191 and 202192. Whole cells were able to convert 10-DAB into 4,10-DDAB (4-deacetyl-10-deacetylbaccatin III) in 90% yield. The enzyme activity in these strains was not effective with paclitaxel and 10-deacetylpaclitaxel, although 4,10-DDAB was produced from baccatin III. The activity in these strains was associated with an insoluble fraction of cell extracts. Several additional isolates were obtained that were identified as variants of Stenotrophomonas maltophilia, and a soluble C-4 deacetylase was purified approx. 218-fold from one of them. The activity of this enzyme was limited to 10-DAB, and the enzyme was not effective with paclitaxel or baccatin III.

Acetylation↗

PubMed1989

Purification and characterization of 4-methylmuconolactone methyl-isomerase, a novel enzyme of the modified 3-oxoadipate pathway in nocardioform actinomycetes.

The novel enzyme 4-methyl-2-enelactone methyl-isomerase was detected in, and purified to electrophoretic homogeneity from, p-toluate-grown cells of Rhodococcus rhodocrous N75, a nocardioform actinomycete. The enzyme was very thermostable and had a native Mr of 75,500; as the monomer had an Mr of 17,000, the enzyme is probably tetrameric. The new isomerase is highly specific with respect to its lactone substrate, only accepting (+)-(4S)-4-methylmuconolactone (4-carboxymethyl-4-methylbut-2-en-1,4-olide), and the putative isomerization reaction intermediate 1-methylbislactone ((-)-1-methyl-3,7-dioxo-2,6-dioxabicyclo-[3.3.0]octane) as substrates, and yielding (-)-(4S)-3-methylmuconolactone (4-carboxymethyl-3-methylbut-2-en-1,4-olide) as product. Some other lactone analogues acted as competitive inhibitors. Our data suggest that the isomerization does not involve actual methyl migration, but proceeds via the 1-methybislactone.

Chromatography, Gel↗

PubMed2001

Application of radiolabeled tracers to biocatalytic flux analysis.

Radiolabeled tracers can provide valuable information about the structure of and flux distributions in biocatalytic reaction networks. This method derives from prior studies of glucose metabolism in mammalian systems and is implemented by pulsing a culture with a radiolabeled metabolite that can be transported into the cells and subsequently measuring the radioactivity of all network metabolites following separation by liquid chromatography. Intracellular fluxes can be directly determined from the transient radioactivity count data by tracking the depletion of the radiolabeled metabolite and/or the accompanying accumulation of any products formed. This technique differs from previous methods in that it is applied within a systems approach to the problem of flux determination. It has been used for the investigation of the indene bioconversion network expressed in Rhodococcus sp. KY1. Flux estimates obtained by radioactive tracers were confirmed by macroscopic metabolite balancing and showed that indene oxidation in steady state chemostat cultures proceeds primarily through a monooxygenase activity forming (1S,2R)-indan oxide, with no dehydrogenation of trans-(1R,2R)-indandiol. These results confirmed the significance of indan oxide formation and identified the hydrolysis of indan oxide as a key step in maximizing the production of (2R)-indandiol, a chiral precursor of the HIV protease inhibitor, Crixivan.

Carbon Radioisotopes↗

PubMed1999

Effect of a mixed culture on co-oxidation during the degradation of saturated hydrocarbon mixture.

Two bacterial strains, Pseudomonas aeruginosa K1 and Rhodococcus equi P1, were used to degrade cyclo-alkanes (such as decalin) by a co-oxidation mechanism. Both strains possessed the capacity to degrade a broad range of n-alkane mixtures (C7 to C28) within 24 h of incubation. Strain P1 rapidly degraded 10 gl-1 pristane within 24 h of incubation (mu = 0.36 h-1 and Yx/s = 0.6). The addition of hexadecane as a growth substrate (above 0.5%, v/v) resulted in complete degradation of 1% (v/v) decalin by strain P1 via a co-oxidation mechanism. Co-oxidation to degrade decalin or pristane by strain K1 proved unsuccessful. Strain P1 was able to degrade decalin totally in a saturated hydrocarbon mixture. Strain K1 was only able to degrade hexadecane from the hydrocarbon mixture, but its degradation rate was higher than that of strain P1. Therefore, there was competition for the hexadecane needed to co-oxidize decalin. As a result, degradation of the hydrocarbon mixture, especially decalin, was incomplete in a mixed culture of strain P1 and K1. Serial addition of hexadecane (twice) allowed complete degradation of the remaining decalin by strain P1. Also, the biodegradation rate of the hydrocarbon mixture by a microbial population from gasoline-contaminated soil was delayed by addition of strain K1 to the population, while the addition of strain P1 resulted in an increase in the biodegradation rate.

Alkanes↗

PubMed2002

Pharmacokinetics of azithromycin in foals after i.v. and oral dose and disposition into phagocytes.

The properties of azithromycin suggest that it may be an alternative to erythromycin for treatment of Rhodococcus equi pneumonia in foals. To investigate this possibility, the disposition of azithromycin in plasma, polymorphonuclear leukocytes (PMN), and alveolar cells was examined after a single administration in foals. Azithromycin suspension was administered orally (p.o.) at a dose of 10 mg/kg to five healthy 2-3-month-old foals. Two weeks later, azithromycin for injection was administered by intravenous (i.v.) infusion at a dose of 5 mg/kg to the same foals. Plasma samples were collected after p.o. and i.v. administration. Peripheral blood PMN and bronchoalveolar lavage fluid and alveolar cells were collected after p.o. administration. Azithromycin concentrations were determined by reverse-phase high-performance liquid chromatography (HPLC) with coulometric electrochemical detection. Azithromycin p.o. absorption was variable with a mean systemic availability of 39% (+/-20%). The plasma half-life was 16 and 18.3 h after i.v. and p.o. administration, respectively. Azithromycin had a very large volume of distribution (V(d)) of 11.6 L/kg [V(d(ss))] and 12.4 L/kg [V(d(area))]. The large V(d) can be attributed to high tissue and intracellular concentrations, exhibited by the high concentration of azithromycin in PMN and alveolar cells. The PMN half-life was 49.2 h. Dosage of 10 mg/kg of azithromycin p.o. once daily for foals with R. equi pneumonia is recommended for further study.

Actinomycetales Infections↗

PubMed2002

Disposition of oral clarithromycin in foals.

Clarithromycin offers numerous advantages over erythromycin and thus, is an attractive alternative for the treatment of Rhodococcus equi infections in foals. The disposition of clarithromycin was investigated in 6 foals after intragastric administration at a dose of 10 mg/kg body weight. Detectable serum concentrations of clarithromycin were found in 3 of 6 foals at 10 minutes and in all foals by 20 minutes post-administration. Time to peak serum concentration (Tmax) was 1.5 hours and peak serum concentration (Cmax) was 0.92+/-0.17 microg/ml. Mean serum concentrations decreased to 0.03 microg/ml at 24 h. No adverse reactions were noted during or after IG administration in any of the foals. Based on the pharmacokinetic parameters, the MIC90 of R. equi isolates, and predicted steady state concentrations, an oral dose of 7.5 mg/kg given every 12 hours would appear appropriate for the treatment of R. equi infections in foals.

Actinomycetales Infections↗