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PubMed2001

Kinetic analysis of microbial desulfurization of model and light gas oils containing multiple alkyl dibenzothiophenes.

The reaction mechanism of biodesulfurization was investigated using whole cells of Rhodococcus erythropolis KA2-5-1, which have the ability to convert dibenzothiophene (DBT) into 2-hydroxybiphenyl. The desulfurization patterns of alkyl DBTs were represented by the Michaeis-Menten equation. The values of rate constants, the limiting maximal velocity (Vmax) and Michaelis constant (Km), for desulfurization of alkyl DBTs were calculated. The relative desulfurization activities of various alkyl DBTs were reduced in proportion to the total carbon numbers of alkyl substituent groups. Alkyl DBTs that had a total of six carbons of alkyl substituent groups were not desulfurized. The type or position of alkyl substituent groups had little effect on desulfurization activity. The desulfurization activity of each alkyl DBT, when mixed together, was reduced. This phenomenon was caused by apparent competitive inhibition of substrates. Using the apparent competitive inhibition model, the desulfurization pattern of a multiple components system containing alkyl DBTs was elucidated. This model was also applicable for biodesulfurization of light gas oil.

Biodegradation, Environmental↗

PubMed2004

Thermostable flavin reductase that couples with dibenzothiophene monooxygenase, from thermophilic Bacillus sp. DSM411: purification, characterization, and gene cloning.

Flavin reductase is essential for the oxygenases involved in microbial dibenzothiophene (DBT) desulfurization. An enzyme of the thermophilic strain, Bacillus sp. DSM411, was selected to couple with DBT monooxygenase (DszC) from Rhodococcus erythropolis D-1. The flavin reductase was purified to homogeneity from Bacillus sp. DSM411, and the native enzyme was a monomer of M(r) 16 kDa. Although the best substrates were flavin mononucleotide and NADH, the enzyme also used other flavin compounds and acted slightly on nitroaromatic compounds and NADPH. The purified enzyme coupled with DszC and had a ferric reductase activity. Among the flavin reductases so far characterized, the present enzyme is the most thermophilic and thermostable. The gene coded for a protein of 155 amino acids with a calculated mass of 17,325 Da. The enzyme was overproduced in Escherichia coli, and the specific activity in the crude extracts was about 440-fold higher than that of the wild-type strain, Bacillus sp. DSM411.

Bacillus↗

PubMed2005

The two-phase water/silicon oil bioreactor prospects in off-gas treatment.

Research was carried out to develop a biphasic biologic reactor able to clean the gas effluents polluted by volatile organic compounds. Initially, Rhodococcus erythropolis T 902.1 was selected on the basis of its capacity to degrade isopropylbenzene (IPB). The effect of gas flow and IPB concentration on the biodegradation of IPB was evaluated. The results show that the use of silicon oil allows large quantities of IPB to be absorbed within the medium of biologic abatement. On the other hand, the biodegradation rate was directly correlated to the inlet flow of IPB. Thus, the reactor presents interesting opportunities for the biologic treatment of gas effluents.

Air Pollutants↗

PubMed2001

Dissemination of catabolic plasmids among desiccation-tolerant bacteria in soil microcosms.

The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trichloroethene and isopropylbenzene degradation pathways, was used as the inoculum, no transconjugant was isolated but the strain remained in the soil. This plasmid had a narrow host range. Pseudomonas putida strain C8S3 was used as the inoculum in a second approach. It bore a broad host range conjugative plasmid harboring a natural transposon, RP4::Tn4371, responsible for biphenyl and 4-chlorobiphenyl degradation pathways. The inoculating population slowly decreased from its original level (10(6) colony-forming units [CFU]/g of dry soil) to approx 3 x 10(2) CFU/g of dry soil after 3 wk. Transconjugant populations degrading biphenyl appeared in constant humidity soil (up to 2 x 10(3) CFU/g) and desiccating soil (up to 10(4) CFU/g). The feasibility of plasmid dissemination as a bioaugmentation technique was demonstrated in desiccating soils. The ecologic significance of desiccation in bioaugmentation was demonstrated: it upset the microbial ecology and the development of transconjugants.

Bacteria↗

PubMed2004

Enhancement of phenanthrene solubilization and biodegradation by trehalose lipid biosurfactants.

Effects of trehalose lipid biosurfactants produced by Rhodococcus erythropolis on the solubilization and biodegradation of phenanthrene (PHE) were investigated. Based on surface tension measurements, the average critical micelle concentration (CMC) of trehalose lipids was determined to be approximately 16 mg total organic carbon (TOC)/L. In solubilization assays, the addition of biosurfactants at 20-fold the CMC increased the apparent solubility of PHE by more than 30-fold. Using a known PHE degrader (isolate P5-2), batch PHE biodegradation experiments were conducted, with and without trehalose lipids, in three systems: Water (devoid of soil solids), soil (Kenansville loamy sand having 0.72% organic matter), and soil-water slurry. Addition of trehalose lipids at 10-fold the CMC enhanced both the rate and the extent of PHE mineralization by isolate P5-2 in the liquid culture. The addition of biosurfactant (32.2 mg TOC/kg soil) to the soil system also increased both the initial rate (by more than twofold) and the extent of PHE mineralization. Biosurfactants increased the rate, but not the extent, of PHE mineralization in the soil-water slurry. The results obtained in the present study indicate that the trehalose lipid biosurfactants produced by R. erythropolis have good solubilization capacity for hydrophobic organic compounds and great potential for applications in bioremediation of sites contamination with polycyclic aromatic hydrocarbons.

Biodegradation, Environmental↗

PubMed2005

Aging of triazine amine in soils demonstrated through sorption, desorption, and bioavailability measurements.

The aging of triazine amine in soil was studied during a time course of 119 d by measuring bioavailability in terms of mineralization after inoculation of the triazine amine-degrading bacterium Rhodococcus erythropolis TA57. The bioavailability was measured in four soil samples: A-, B-, and C-horizons from an agricultural soil profile and in a peat soil. The sorption of triazine amine in the soil samples was quantified during the period of aging in terms of sorption distribution coefficients (Kd) and desorption distribution coefficients (Kd,des). Measures of bioavailability and triazine amine concentration in the nonavailable fraction showed effects of aging in the soils that were rich in organic matter. The triazine amine bioavailability declined significantly during the aging period in soils containing greater than 2% organic carbon, whereas the B- and C-horizons showed no signs of aging, in agreement with their low content of organic material. Corresponding to this, desorption decreased significantly in the A-horizon but, surprisingly, not in the peat soil. Analyses by thin-layer chromatography indicated an association of aqueous triazine amine and dissolved organic matter in the peat soil. This gives an explanation for both the significant decrease in bioavailability and the noncorresponding stability of the nonavailable (i.e., nondesorbed) fraction.

Adsorption↗

PubMed2005

Sorption of hydrophobic organic chemicals to bacteria.

The toxicity and time-dependent sorption of three hydrophobic organic chemicals to Rhodococcus rhodochrous bacteria were investigated. In experiments, environmentally relevant concentrations of pentachlorophenol (PCP), hexachlorobenzene (HCB), and dichlorobiphenyl (DPCB) were applied to living (both growing and nongrowing) bacteria as well as to dead bacteria. For PCP (an ionizing chemical), bacterial growth decreased, and bacterial death increased, as the PCP concentration increased. In sorption experiments with PCP, the partition coefficient was affected by the active uptake of PCP by living but not by dead bacteria, by the death of the living bacteria because of PCP toxicity, and by saturation of site-specific sorption as the PCP concentration increased. Hexachlorobenzene (a nonionizing chemical) did not affect bacterial growth or death at all HCB concentrations investigated. In sorption experiments with HCB, the partition coefficient depended on the rate of bacterial growth relative to the sorption rate. The sorption rate depended on the state of bacterial aggregation, and this changed with time. Results for DPCB (a nonionizing chemical with an equilibrium partition coefficient similar to that of HCB) were similar to those for HCB.

Absorption↗

PubMed1990

Infected wounds and repeated septicemia in a case of factitious illness.

During 19 years an assistant nurse, now 35 years old, has been repeatedly treated for several malingered and self-induced disorders escalating to self-mutilation. An ulcer of her right leg never epithelialised in spite of various local treatments and surgical intervention. During repeated attacks of self-induced septicemia altogether 11 different bacterial species were isolated; on 8 occasions Rhodococcus equi. The septicemias were successfully treated with antibiotics. The underlying psychiatric problem, a borderline personality disorder, has not been possible to treat in a conventional manner. Probably due to collaboration between the plastic surgeon and the psychiatrist she has had fewer attendances and shorter hospital stays lately. Her prognosis is still dubious as regards further self-mutilation and other expressions of self-destructive behaviour.

Actinomycetales Infections↗

PubMed1994

A highly unusual combination of pulmonary pathogens in an HIV infected patient.

We report on a case with an unusual combination of pulmonary pathogens including Pneumocystis carinii, Rhodococcus equi and Toxoplasma gondii in an HIV infected patient. The multiple microbiological procedures required to ascertain the etiological diagnoses of pneumonitis in HIV-seropositive subjects are discussed.

AIDS-Related Opportunistic Infections↗

PubMed1990

Pulmonary malacoplakia in a child.

Pulmonary malacoplakia is a rare condition with only five previously reported cases in the literature, all occurring in adults. We describe a case of malacoplakia of the lung in a 6-year-old female with acute lymphoblastic leukemia in remission and a Rhodococcus equi pneumonia and septicemia. The case demonstrates that pulmonary malacoplakia can occur in immunocompromised pediatric patients and that malacoplakia should, therefore, be added to the list of causes of nodular lung infiltrates in immunocompromised children.

Child↗

PubMed1992

Transformation of an insect symbiont and expression of a foreign gene in the Chagas' disease vector Rhodnius prolixus.

A shuttle plasmid was developed that is capable of replicating both in Escherichia coli and in Rhodococcus rhodnii, a bacterial symbiont of the Chagas' disease vector Rhodnius prolixus. We have been able to transform R. rhodnii with this plasmid, infect aposymbiotic R. prolixus with the transformed symbionts, select with the antibiotic thiostrepton, and re-isolate genetically altered symbionts from the insects following successive molts. Symbiotic bacteria are potentially valuable as vehicles for the stable introduction of foreign genes into insects with the goal of eventually altering the ability of the insect to transmit a pathogenic agent.

Animals↗

PubMed1998

Granuloma formation and in vitro macrophage activation in mice by mycoloyl glycolipids from Nocardia asteroides and related taxa.

Cord factor (trehalose 6,6'-dimycolate: TDM) is a well-known toxic glycolipid in Mycobacterium tuberculosis. We isolated various mycoloyl glycolipids from Nocardia asteroides 23,167 and related species which are closely related taxonomically to Mycobacterium. Since Nocardia is also an opportunistic pathogen co-infected with HIV, we examined in vivo granuloma formation and the in vitro macrophage activation in mice. We found that cord factor (TDM) and glucose monomycolate (GM) from Nocardia asteroides and Rhodococcus species with shorter chain mycolic acids also exhibited distinctive granuloma-forming activity in lungs, spleen and liver in mice and in vitro induction of prostaglandin E2 (PGE2) and interleukin 1 (IL-1) synthesis. We also found that mycoloyl glycolipids possessing trehalose or glucose as a carbohydrate moiety exhibited immunomodulatory activity, and that mycoloyl glycolipids with longer chain mycolic acids exhibited stronger activity in mice than did those with shorter chain mycolic acids. The mycoloyl glycolipids from Nocardia asteroides directly activated macrophages. Stimulation of above concentration with 0.16 microgram/ml of TDM or 0.8 microgram/ml of GM markedly enhanced production of PGE2 by mouse peritoneal macrophages. At higher concentrations above 100 micrograms/ml of TDM or 500 micrograms/ml of GM, IL-1 release was also enhanced.

Animals↗

PubMed1999

Characterization of antarctic hydrocarbon-degrading bacteria capable of producing bioemulsifiers.

During screening for biosurfactant-producing, n-alkane-degrading marine bacteria, two heterotrophic bacterial strains were isolated from enriched mixed cultures, obtained from Terra Nova Bay (Ross sea, Antarctica) by using aliphatic and artomatic hydrocarbons as the principal carbon source. These gram-positive, aerobic, cocci-shaped bacteria use a various number of organic compounds, including aliphatic hydrocarbons, volatile fatty acids, and biphenyl. During cultivation on n-alkanes as sole source of carbon and energy, all strains produced both an extracellular and cell-bound surface-active mixture of trehalose lipids which reduced the surface tension of water from 72 mN/m to 32mN/m. This class of glycolipids was found to be produced only by marine rhodococci. The 16S-rRNA gene sequence analysis showed that both strains are members of the G + C rich gram-positive group of the phylum Proteobacteria and was found to be almost identical to that of Rhodococcus fascians DSM 20669. The potential of these strains for in situ bioremediation of contaminated cold marine environment is discussed in the present study.

Alkanes↗

PubMed1999

TNF receptor p55 is required for elimination of inflammatory cells following control of intracellular pathogens.

The elimination of lymphocytes within inflammatory lesions is a critical component in the resolution of disease once pathogens have been cleared. We report here that signaling through the TNF receptor p55 (TNFRp55) is required to eliminate lymphocytes from lesions associated with intracellular pathogens. Thus, TNFRp55-/- mice, but not Fas-deficient mice, maintained inflammatory lesions associated with either Leishmania major or Rhodococcus equi infection, although they developed a Th1 response and controlled the pathogens. Inflammatory cells from either L. major- or R. equi-infected C57BL/6 mice were sensitive to TNF-induced apoptosis, and conversely the number of apoptotic cells in the lesions from TNFRp55-/- mice was dramatically reduced compared with wild-type mice. Furthermore, in vivo depletion of TNF in wild-type mice blocked lesion regression following R. equi infection. Taken together, our results suggest that signaling through the TNFRp55, but not Fas, is required to induce apoptosis of T cells within inflammatory lesions once pathogens are eliminated, and that in its absence lesions fail to regress.

Actinomycetales Infections↗

PubMed1999

Bacterial degradation of hydrocarbons as evidenced by respirometric analysis.

The microbial biodegradability of mineral oil and other hydrocarbons, namely hexane, decane and tetradecane was determined using the Warburg constant volume respirometer. Results of oxygen uptake indicated that hexane and tetradecane were more degradable than mineral oil and decane. Rhodococcus erythropolis and Erwinia cancerogena showed the highest (0.866) and lowest (0.115) oxygen quotient (Qo2) values, respectively, when exposed to mineral oil. Staphylococcus warneri and Enterobacter cloacae showed the highest (2.895) and (2.816) Qo2 values, respectively, when exposed to hexane; whereas E. cloacae and E. cancerogena showed the lowest Qo2 values (1.289 and 1.824), respectively. Both R. erythropolis and E. cloacae had the highest Qo2 values (2.859 and 2.289), respectively, when exposed to tetradecane. More oxygen was consumed by R. erythropolis than the other bacterial cultures when exposed to all hydrocarbons. In contrast, less oxygen was taken by E. cancerogena than the other bacterial cultures when exposed to all hydrocarbons, except for hexane.

Alkanes↗

PubMedDate not supplied

[Dependence of transformation of chlorophenols by Rhodococci on position and number of chlorine atoms in the aromatic ring].

Study of the conversion of chlorophenols by Rhodococcus opacus 1G, R. rhodnii 135, R. rhodochrous 89, and R. opacus 1cp disclosed the dependence of the conversion rate and pathway on the number and position of chlorine atoms in the aromatic ring. The most active chlorophenol converter, strain R. opacus 1cp, grew on each of the three isomeric monochlorophenols and on 2,4-dichlorophenol; the rate of growth decreased from 4-chlorophenol to 3-chlorophenol and then to 2-chlorophenol. The parameters of growth on 2,4-dichlorophenol were the same as on 3-chlorophenol. None of the strains studied utilized trichlorophenols. A detailed study of the pathway of chlorophenol transformation showed that 3-chloro-, 4-chloro-, and 2,4-dichlorophenol were utilized by the strains via a modified ortho-pathway. 2-Chlorophenol and 2,3-dichlorophenol were transformed by strains R. opacus 1cp and R. rhodochrous 89 via corresponding 3-chloro- and 3,4-dichloropyrocatechols, which were then hydroxylated with the formation of 4-chloropyrogallol and 4,5-dichloropyrogallol; this route had not previously been described in bacteria. Phenol hydroxylase of R. opacus 1G exhibited a previously undescribed catalytic pattern, catalyzing oxidative dehalogenation of 2,3,5-trichlorophenol with the formation of 3,5-dichloropyrocatechol but not hydroxylation of the nonsubstituted position 6.

Biotransformation↗

PubMed2000

Room-temperature ionic liquids as replacements for organic solvents in multiphase bioprocess operations.

Organic solvents are widely used in a range of multiphase bioprocess operations including the liquid-liquid extraction of antibiotics and two-phase biotransformation reactions. There are, however, considerable problems associated with the safe handling of these solvents which relate to their toxic and flammable nature. In this work we have shown for the first time that room-temperature ionic liquids, such as 1-butyl-3-methylimi- dazolium hexafluorophosphate, [bmim][PF(6)], can be successfully used in place of conventional solvents for the liquid-liquid extraction of erythromycin-A and for the Rhodococcus R312 catalyzed biotransformation of 1, 3-dicyanobenzene (1,3-DCB) in a liquid-liquid, two-phase system. Extraction of erythromycin with either butyl acetate or [bmim][PF(6)] showed that values of the equilibrium partition coefficient, K, up to 20-25 could be obtained for both extractants. The variation of K with the extraction pH was also similar in the pH range 5-9 though differed significantly at higher pH values. Biotransformation of 1,3-DCB in both water-toluene and water-[bmim][PF(6)] systems showed similar profiles for the conversion of 1,3-DCB initially to 3-cyanobenzamide and then 3-cyanobenzoic acid. The initial rate of 3-cyanobenzamide production in the water-[bmim][PF(6)] system was somewhat lower, however, due to the reduced rate of 1,3-DCB mass transfer from the more viscous [bmim] [PF(6)] phase. It was also shown that the specific activity of the biocatalyst in the water-[bmim] [PF(6)] system was almost an order of magnitude greater than in the water-toluene system which suggests that the rate of 3-cyanobenzamide production was limited by substrate mass transfer rather than the activity of the biocatalyst.

Anti-Bacterial Agents↗

PubMed2000

Enzymatic dehalogenation of gas phase substrates with haloalkane dehalogenase.

Haloalkane dehalogenase is an enzyme capable of catalyzing the conversion of short-chained (C(2)-C(8)) aliphatic halogenated hydrocarbons to a corresponding primary alcohol. Because of its broad substrate specificity for mono-, di-, and trisubstituted halogenated hydrocarbons and cofactor independence, haloalkane dehalogenases are attractive biocatalysts for gas-phase bioremediation of pollutant halogenated vapor emissions. A solid preparation of haloalkane dehalogenase from Rhodococcus rhodochrous was used to catalyze the dehalogenation reaction of 1-chlorobutane or 1,3-dichloropropane delivered in the gas phase. For optimal gas-phase dehalogenase activity, a relative humidity of 100%, a(w) = 1, was desired. With a 50% reduction in the vapor-phase hydration level, an 80% decrease in enzymatic activity was observed. The enzyme kinetics for the gas-phase substrates obeyed an Arrhenius-"like" behavior and the solid haloalkane dehalogenase preparation was more thermally stable than its water-soluble equivalent. Triethylamine was added to the gaseous reaction environment in efforts to increase the rate of reaction. A tenfold increase in the dehalogenase activity for the vapor-phase substrates was observed with the addition of triethylamine. Triethylamine altered the electrostatic environment of haloalkane dehalogenase via a basic shift in local pH, thereby minimizing the effect of the pH-reducing reaction product on enzyme activity. Both organic phase and solid-state buffers were used to confirm the activating role of the altered ionization state.

Air Pollutants↗