Pathway,inhibition and regulation of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether oxidation in a filamentous fungus, <Emphasis Type="Italic">Graphium</Emphasis> sp.

The filamentous fungus Graphium sp. (ATCC 58400) co-metabolically oxidizes the gasoline oxygenate methyl tertiary butyl ether (MTBE) after growth on gaseous n-alkanes. In this study, the enzymology and regulation of MTBE oxidation by propane-grown mycelia of Graphium sp. were further investigated and defined. The trends observed during MTBE oxidation closely resembled those described for propane-grown cells of the bacterium Mycobacterium vaccae JOB5. Propane-grown mycelia initially oxidized the majority (∼95%) of MTBE to tertiary butyl formate (TBF), and this ester was biotically hydrolyzed to tertiary butyl alcohol (TBA). However, unlike M. vaccae JOB5, our results collectively suggest that propane-grown mycelia only have a limited capacity to degrade TBA. None of the products of MTBE exerted a physiologically relevant regulatory effect on the rate of MTBE or propane oxidation, and no significant effect of TBA was observed on the rate of TBF hydrolysis. Together, these results suggest that the regulatory effects of MTBE oxidation intermediates proposed for MTBE-degrading organisms such as Mycobacterium austroafricanum are not universally relevant mechanisms for MTBE-degrading organisms. The results of this study are discussed in terms of their impact on our understanding of the diversity of aerobic MTBE-degrading organisms and pathways and enzymes involved in these processes.     

Methyl <Emphasis Type="Italic">tert</Emphasis>-butyl Ether and <Emphasis Type="Italic">tert</Emphasis>-butyl Alcohol Degradation by <Emphasis Type="Italic">Fusarium solani</Emphasis>

Fusarium solani degraded methyl tert-butyl ether (MTBE) and other oxygenated compounds from gasoline including tert-butyl alcohol (TBA). The maximum degradation rate of MTBE was 16 mg protein h and 46 mg/g protein h for TBA. The culture transformed 77% of the total carbon to ¹⁴CO₂. The estimated yield for MTBE was 0.18 g dry wt/g MTBE.     

The mutagenicity testing of tertiary-butyl alcohol, tertiary-butyl acetate™ and methyl tertiary-butyl ether in Salmonella typhimurium

Tertiary-Butyl alcohol (TBA), tertiary-butyl acetate™ (TBAc™) and methyl tertiary-butyl ether (MTBE) are chemicals to which the general public may be exposed either directly or as a result of their metabolism. There is little evidence that they are genotoxic; however, an earlier publication reported that significant results were obtained in Salmonella typhimurium TA102 mutagenicity tests with both TBA and MTBE. We now present results of testing these chemicals and TBAc™ against S. typhimurium strains in two laboratories. The emphasis was placed on testing with S. typhimurium TA102 and the use of both dimethyl sulphoxide and water as vehicles. Dose levels up to 5000 μg/plate were used and incubations were conducted in both the presence and absence of liver S9 prepared from male rats treated with either Arochlor 1254 or phenobarbital-β-naphthoflavone. The experiments were replicated, but in none of them was a significant mutagenic response observed, thus the current evidence indicates the TBA, TBAc™ and MTBE are not mutagenic in bacteria.     

<Emphasis Type="Italic">n</Emphasis>-Alkane assimilation and <Emphasis Type="Italic">tert</Emphasis>-butyl alcohol (TBA) oxidation capacity in <Emphasis Type="Italic">Mycobacterium austroafricanum</Emphasis> strains

Mycobacterium austroafricanum IFP 2012, which grows on methyl tert-butyl ether (MTBE) and on tert-butyl alcohol (TBA), the main intermediate of MTBE degradation, also grows on a broad range of n-alkanes (C₂ to C₁₆). A single alkB gene copy, encoding a non-heme alkane monooxygenase, was partially amplified from the genome of this bacterium. Its expression was induced after growth on n-propane, n-hexane, n-hexadecane and on TBA but not after growth on LB. The capacity of other fast-growing mycobacteria to grow on n-alkanes (C₁ to C₁₆) and to degrade TBA after growth on n-alkanes was compared to that of M. austroafricanum IFP 2012. We studied M. austroafricanum IFP 2012 and IFP 2015 able to grow on MTBE, M. austroafricanum IFP 2173 able to grow on isooctane, Mycobacterium sp. IFP 2009 able to grow on ethyl tert-butyl ether (ETBE), M. vaccae JOB5 (M. austroaafricanum ATCC 29678) able to degrade MTBE and TBA and M. smegmatis mc2 155 with no known degradation capacity towards fuel oxygenates. The M. austroafricanum strains grew on a broad range of n-alkanes and three were able to degrade TBA after growth on propane, hexane and hexadecane. An alkB gene was partially amplified from the genome of all mycobacteria and a sequence comparison demonstrated a close relationship among the M. austroafricanum strains. This is the first report suggesting the involvement of an alkane hydroxylase in TBA oxidation, a key step during MTBE metabolism.     

<Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K, <Superscript>238</Superscript>Pu, <Superscript>239+240</Superscript>Pu and <Superscript>90</Superscript>Sr in biological samples from King George Island (Southern Shetlands) in Antarctica

There are few data reported on radionuclide contamination in Antarctica. The aim of this paper is to report ¹³⁷Cs, ⁹⁰Sr and ^238,239+240Pu and ⁴⁰K activity concentrations measured in biological samples collected from King George Island (Southern Shetlands, Antarctica), mostly during 2001–2002. The samples included: bones, eggshells and feathers of penguin Pygoscelis papua, bones and feathers of petrel Daption capense, bones and fur of seal Mirounga leonina, algae Himantothallus grandifolius, Desmarestia anceps and Cystosphaera jacquinotii, fish Notothenia corriceps, sea invertebrates Amphipoda, shells of limpet Nacella concina, lichen Usnea aurantiaco-atra, vascular plants Deschampsia antarctica and Colobanthus quitensis, fungi Omphalina pyxidata, moss Sanionia uncinata and soil. The results show a large variation in some activity concentrations. Samples from the marine environment had lower contamination levels than those from terrestrial ecosystems. The highest activity concentrations for all radionuclides were found in lichen and, to a lesser extent, in mosses, probably because lichens take up atmospheric pollutants and retain them. The only significant correlation (except for that expected between ²³⁸Pu and ^239+240Pu) was noted for moss and lichen samples between plutonium and ⁹⁰Sr. A tendency to a slow decrease with time seems to be occurring. Analyses of the activity ratios show varying fractionation between various radionuclides in different organisms. Algae were relatively more highly contaminated with plutonium and radiostrontium, and depleted with radiocesium. Feathers had the lowest plutonium concentrations. Radiostrontium and, to a lesser extent, Pu accumulated in bones. The present low intensity of fallout in Antarctic has a lower ²³⁸Pu/^239+240Pu activity ratio than that expected for global fallout.     

Effects of gasoline components on MTBE and TBA cometabolism by <Emphasis Type="Italic">Mycobacterium austroafricanum</Emphasis> JOB5

In this study we have examined the effects of individual gasoline hydrocarbons (C_5–10,12,14 n-alkanes, C_5–8 isoalkanes, alicyclics [cyclopentane and methylcyclopentane] and BTEX compounds [benzene, toluene, ethylbenzene, m-, o-, and p-xylene]) on cometabolism of methyl tertiary butyl ether (MTBE) and tertiary butyl alcohol (TBA) by Mycobacterium austroafricanum JOB5. All of the alkanes tested supported growth and both MTBE and TBA oxidation. Growth on C_5–8 n-alkanes and isoalkanes was inhibited by acetylene whereas growth on longer chain n-alkanes was largely unaffected by this gas. However, oxidation of both MTBE and TBA by resting cells was consistently inhibited by acetylene, irrespective of the alkane used as growth-supporting substrate. A model involving two separate but co-expressed alkane-oxidizing enzyme systems is proposed to account for these observations. Cyclopentane, methylcyclopentane, benzene and ethylbenzene did not support growth but these compounds all inhibited MTBE and TBA oxidation by alkane-grown cells. In the case of benzene, the inhibition was shown to be due to competitive interactions with both MTBE and TBA. Several aromatic compounds (p-xylene > toluene > m-xylene) did support growth and cells previously grown on these substrates also oxidized MTBE and TBA. Low concentrations of toluene (<10 μM) stimulated MTBE and TBA oxidation by alkane-grown cells whereas higher concentrations were inhibitory. The effects of acetylene suggest strain JOB5 also has two distinct toluene-oxidizing activities. These results have been discussed in terms of their impact on our understanding of MTBE and TBA cometabolism and the enzymes involved in these processes in mycobacteria and other bacteria.     

Estimation of the fraction of biologically active methyl <Emphasis Type="Italic">tert</Emphasis>-butyl ether degraders in a heterogeneous biomass sample

The fraction of biologically active methyl tert-butyl ether degraders in reactors is just as important for prediction of removal rates as knowledge of the kinetic parameters. The fraction of biologically active methyl tert-butyl ether degraders in a heterogeneous biomass sample, taken from a packed bed reactor, was determined using a batch kinetic based approach. The procedure involved modeling of methyl tert-butyl ether removal rates from batch experiments followed by parameter estimations. It was estimated to be 5–14% (w/w) of the measured volatile suspended solids concentration in the reactor.     

Biodegradation of methyl <Emphasis Type="Italic">tert</Emphasis>-butyl ether by cold-adapted mixed and pure bacterial cultures

An aerobic mixed bacterial culture (CL-EMC-1) capable of utilizing methyl tert-butyl ether (MTBE) as the sole source of carbon and energy with a growth temperature range of 3 to 30°C and optimum of 18 to 22°C was enriched from activated sludge. Transient accumulation of tert-butanol (TBA) occurred during utilization of MTBE at temperatures from 3°C to 14°C, but TBA did not accumulate above 18°C. The culture utilized MTBE at a concentration of up to 1.5 g l⁻¹ and TBA of up to 7 g l⁻¹. The culture grew on MTBE at a pH range of 5 to 9, with an optimum pH of 6.5 to 7.1. The specific growth rate of the CL-EMC-1 culture on 0.1 g l⁻¹ of MTBE at 22°C and pH 7.1 was 0.012 h⁻¹, and the growth yield was 0.64 g (dry weight) g⁻¹. A new MTBE-utilizing bacterium, Variovorax paradoxus strain CL-8, isolated from the mixed culture utilized MTBE, TBA, 2-hydroxy isobutyrate, lactate, methacrylate, and acetate as sole sources of carbon and energy but not 2-propanol, acetone, methanol, formaldehyde, or formate. Two other isolates, Hyphomicrobium facilis strain CL-2 and Methylobacterium extorquens strain CL-4, isolated from the mixed culture were able to grow on C₁ compounds. The combined consortium could thus utilize all of the carbon of MTBE.     

Biodegradation of methyl <Emphasis Type="Italic">t</Emphasis>-butyl ether by aerobic granules under a cosubstrate condition

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) with ethanol as a cosubstrate were successfully developed in a well-mixed sequencing batch reactor (SBR). Aerobic granules were first observed about 100 days after reactor startup. Treatment efficiency of MTBE in the reactor during stable operation exceeded 99.9%, and effluent MTBE was in the range of 15–50 μg/L. The specific MTBE degradation rate was observed to increase with increasing MTBE initial concentration from 25 to 500 mg/L, which peaked at 22.7 mg MTBE/g (volatile suspended solids)·h and declined with further increases in MTBE concentration as substrate inhibition effects became significant. Microbial-community deoxyribonucleic acid profiling was carried out using denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S ribosomal ribonucleic acid. The reactor was found to be inhabited by several diverse bacterial species, most notably microorganisms related to the genera Sphingomonas, Methylobacterium, and Hyphomicrobium vulgare. These organisms were previously reported to be associated with MTBE biodegradation. A majority of the bands in the reactor represented a group of organisms belonging to the Flavobacteria–Proteobacteria–Actinobacteridae class of bacteria. This study demonstrates that MTBE can be effectively degraded by aerobic granules under a cosubstrate condition and gives insight into the microorganisms potentially involved in the process.     

Effect of Mn<Superscript>2+</Superscript> augmentation on reinforcing aerobic sludge granulation in a sequencing batch reactor

Two sequencing batch reactors were synchronously operated to investigate the effect of manganese (II) (Mn²⁺) augmentation on aerobic granulation. Reactor 1 (R1) was added with 10 mg/L Mn²⁺, while there was no Mn²⁺ augmentation in reactor 2 (R2). Results showed that R1 had a faster granulation process than R2 and R1 performed better in chemical oxygen demand (COD) and ammonium nitrogen (NH₄⁺–N) removal efficiencies. Moreover, the mature granules augmented with Mn²⁺ behaved better on their physical characteristics and size distributions, and they also had higher production of extracellular polymeric substances (EPS) content. The result of three-dimensional excitation and emission matrix fluorescence showed that Mn²⁺ had the function of causing organic material diversity (especially proteins diversity) in EPS fraction from granules. Polymerase chain reaction and denaturing gradient gel electrophoresis techniques were employed to analyze the microbial and genetic characteristics in mature granules. The results exhibited that Mn²⁺ augmentation was mainly responsible for the higher microbial diversity of granules from R1 compared with that from R2. Uncultured sludge bacterium A16 (AF234726) and Rhodococcus sp. WTZ-R2 (HM004214) were the major species in R1, while only uncultured sludge bacterium A16 (AF234726) in R2. Moreover, there were eight species of organisms found in both two aerobic granules, and three species were found only in aerobic granules from R1. It could be concluded that Mn²⁺ could enhance the sludge granulation process and have a key effect role on the biological properties during the sludge granulation.     

<Superscript>1</Superscript>H NMR metabolic fingerprinting of saffron extracts

The aim of this study was to explore feasibility of ¹H NMR metabolic fingerprinting for discrimination of authenticity of saffron using principal component analysis (PCA) modeling. Authentic reference Iranian saffron (n = 31) and commercial samples (n = 32) were used. Cross-validated PCA models based on ¹H NMR spectra of solutions prepared by direct extraction of grinded saffron with methanol-d ₄ distinguished reference Iranian saffron samples from commercial samples that formed several distinct clusters, some of which represent falsified samples as confirmed by microscopic analysis. The production sites and drying conditions of the authentic reference Iranian samples were not reflected in the current dataset. Picrocrocin and glycosyl esters of crocetin emerged as the most important ¹H NMR markers of authentic saffron by using statistical correlation spectroscopy. In conclusion, ¹H NMR spectra of saffron extracts combined with pattern recognition by PCA provide immediate means of unsupervised classification of saffron samples.     

The dynamic transfer of <Superscript>3</Superscript>H and <Superscript>14</Superscript>C in mammals: a proposed generic model

Associated with the present debate regarding the potential revival of nuclear energy there is an increased interest in assessing the radiological risk to the public and also the environment. Tritium and ¹⁴C are key radionuclides of interest in many circumstances (e.g. heavy water reactors, waste storage and fusion reactors). Because the stable analogues of these two radionuclides are integral to most biological compounds, their modelling should follow general principles from life sciences. In this paper, a model of the dynamics of ¹⁴C and ³H in mammals is proposed on the basis of metabolic understanding and of, as far as possible, readily available data (e.g. for organ composition and metabolism). The model is described together with validation tests (without calibration) for a range of farm animals. Despite simplifications, the model tests are encouraging for a range of animal types and products (tissues and milk), and further improvements are suggested.     

The Comparative and Combined Inhibitory Effects of MTBE and TBA on the Activities of Soil Exoenzymes

Methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) are major soil contaminants, and they have been actively investigated for their toxic effects on living organisms in soil ecosystems. Although previous studies have been used as tools to evaluate the health of soil, they have been limited in scope and ability to analyze the overall microbial activity. In the present study, the effects of MTBE and TBA on the activity of soil exoenzymes including urease, acid phosphatase, arylsulfatase, β-glucosidase, dehydrogenase, and fluorescein diacetate hydrolase, which are involved in nutrient cycles and overall microbial activities, were investigated. Soil samples were treated with 0–2% of MTBE and TBA solutions, and the comparative effects and combined effects on quantity of active soil exoenzymes were determined. The activity of six exoenzymes exposed solely to MTBE and TBA did not significantly change with dose concentration or exposure time, but did show significant changes when exposed to high concentrations of MTBE and TBA combined, with dehydrogenase being the most affected. Therefore, we proposed dehydrogenase as a potential biomarker to assess the risk of co-contamination of MTBE and TBA.     

Simultaneous <Superscript>1</Superscript>H- or <Superscript>2</Superscript>H-, <Superscript>15</Superscript>N- and multiple-band-selective <Superscript>13</Superscript>C-decoupling during acquisition in <Superscript>13</Superscript>C-detected experiments with proteins and oligonucleotides

Significant resolution improvement in ¹³C,¹³C-TOCSY spectra of uniformly deuterated and ¹³C, ¹⁵N-labeled protein and ¹³C,¹⁵N-labeled RNA samples is achieved by introduction of multiple-band-selective ¹³C-homodecoupling applied simultaneously with ¹H- or ²H- and ¹⁵N-decoupling at all stages of multidimensional experiments including signal acquisition period. The application of single, double or triple band-selective ¹³C-decoupling in 2D-[¹³C,¹³C]-TOCSY experiments during acquisition strongly simplifies the homonuclear splitting pattern. The technical aspects of complex multiple-band homonuclear decoupling and hardware requirements are discussed. The use of this technique (i) facilitates the resonance assignment process as it reduces signal overlap in homonuclear ¹³C-spectra and (ii) possibly improves the signal-to-noise ratio through multiplet collapse. It can be applied in any ¹³C-detected experiment.     

Treatment of Groundwater Contaminated with PAHs, Gasoline Hydrocarbons, and Methyl tert-butyl Ether in a Laboratory Biomass-Retaining Bioreactor

In this study, we investigated the treatability of co-mingled groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs), gasoline hydrocarbons, and methyl tert-butyl ether (MtBE) using an ex-situ aerobic biotreatment system. The PAHs of interest were naphthalene, methyl-naphthalene, acenaphthene, acenaphthylene, and carbazole. The gasoline hydrocarbons included benzene, toluene, ethyl benzene, and p-xylene (BTEX). Two porous pot reactors were operated for a period of 10 months under the same influent contaminant concentrations. The contaminated groundwater was introduced into the reactors at a flow rate of 4 and 9 l/day, resulting in a hydraulic retention time (HRT) of 32 and 15 h, respectively. In both reactors, high removal efficiencies were achieved for the PAHs (>99%), BTEX and MtBE (>99.7%). All the PAHs of interest and the four BTEX compounds were detected at concentrations less than 1 μg/l throughout the study duration. Effluent MtBE from both reactors was observed at higher levels; nevertheless, its concentration was lower than the 5 μg/l Drinking Water Advisory for MtBE implemented in California.     

CD133<Superscript>+</Superscript>CD44<Superscript>+</Superscript> subgroups may be human small intestinal stem cells

The identification and separation of small intestinal epithelial stem cells are still on the preliminary stage. In this study, we planned to utilize immunohistochemistry, fluorescence-activated cell sorting (FACS) and RT-PCR to investigate the possibility of CD133 and CD44 as markers of human small intestinal epithelial stem cells. The expressions of CD133, CD44 and Lgr5 were studied by immunohistochemistry. Four subgroups of CD133⁺CD44⁺, CD133⁺CD44⁻, CD133⁻CD44⁺, CD133⁻CD44⁻ were sorted out through FACS and the expression level of Lgr5 gene was measured by RT-PCR and polyacrylamide gel electropheresis (PAGE) with sliver stained. Ten cases of samples were available for analyzing. By immunohistochemical staining, few cells with positive expressions of CD133, CD44 and Lgr5 were distributed in the bottom of crypts with the expression locations somewhat overlapped. The average percentage of CD133⁺CD44⁺ cells was 0.0580 ± 0.0403%, while the corresponding contents of CD133⁺CD44⁻ cells, CD133⁻CD44⁺ cells and CD133⁻CD44⁻ cells were 0.4000 ± 0.1225%, 0.7000 ± 0.2646% and 76.5600 ± 3.5529% respectively. Ten times of positive expressions of Lgr5 were detected in the CD133⁺CD44⁺ groups, while 9/10, 8/10 and 4/10 times for CD133⁺CD44⁻, CD133⁻CD44⁺ and CD133⁻CD44⁻ subgroups respectively. With the help of Quantityone 4.62 software, the densities of corresponding place to Lgr5 and reference gene were obtained. The density ratios of corresponding place to Lgr5 to reference gene were significant difference between subgroups (P < 0.001). By means of LSD method, the density ratios in CD133⁺CD44⁺ subgroups had statistical differences from the other subgroups (P < 0.05). We concluded CD133⁺CD44⁺ cells may be human small intestinal epithelial stem cells, which need further researches to confirm.     

Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> exchange activity in the alkaliphile halotolerant cyanobacterium <Emphasis Type="Italic">Aphanothece halophytica</Emphasis>

The activity of Na⁺/H⁺ exchanger to remove toxic Na⁺ is important for growth of organisms under high salinity. In this study, the halotolerant cyanobacterium Aphanothece halophytica was shown to possess Na⁺/H⁺ exchange activity since exogenously added Na⁺ could dissipate a pre-formed pH gradient, and decrease extracellular pH. Kinetic analysis yielded apparent K _m (Na⁺) and V _max of 20.7 ± 3.1 mM and 3,333 ± 370 nmol H⁺ min⁻¹ mg⁻¹, respectively. For cells grown under salt-stress condition, the apparent K _m (Na⁺) and V _max was 18.3 ± 3.5 mM and 3,703 ± 350 nmol H⁺ min⁻¹ mg⁻¹, respectively. Three cations with decreasing efficiency namely Li⁺, Ca²⁺, and K⁺ were also able to dissipate pH gradient. Only marginal exchange activity was observed for Mg²⁺. The exchange activity was strongly inhibited by Na⁺-gradient dissipators, monensin, and sodium ionophore as well as by CCCP, a protonophore. A. halophytica showed high Na⁺/H⁺ exchange activity at neutral and alkaline pH up to pH 10. Cells grown at pH 7.6 under high salinity exhibited higher Na⁺/H⁺ exchange activity than those grown under low salinity during 15 days of growth suggesting a role of Na⁺/H⁺ exchanger for salt tolerance in A. halophytica. Cells grown at alkaline pH of 9.0 also exhibited a progressive increase of Na⁺/H⁺ exchange activity during 15 days of growth.     

DFT modeling on the suitable crown ether architecture for complexation with Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> metal ions

Crown ether architectures were explored for the inclusion of Cs⁺ and Sr²⁺ ions within nano-cavity of macrocyclic crown ethers using density functional theory (DFT) modeling. The modeling was undertaken to gain insight into the mechanism of the complexation of Cs⁺ and Sr²⁺ ion with this ligand experimentally. The selectivity of Cs⁺ and Sr²⁺ ions for a particular size of crown ether has been explained based on the fitting and binding interaction of the guest ions in the narrow cavity of crown ethers. Although, Di-Benzo-18-Crown-6 (DB18C6) and Di-Benzo-21-Crown-7 (DB21C7) provide suitable host architecture for Sr²⁺ and Cs⁺ ions respectively as the ion size match with the cavity of the host, but consideration of binding interaction along with the cavity matching both DB18C6 and DB21C7 prefers Sr²⁺ ion. The calculated values of binding enthalpy of Cs metal ion with the crown ethers were found to be in good agreement with the experimental results. The gas phase binding enthalpy for Sr²⁺ ion with crown ether was higher than Cs metal ion. The ion exchange reaction between Sr and Cs always favors the selection of Sr metal ion both in the gas and in micro-solvated systems. The gas phase selectivity remains unchanged in micro-solvated phase. We have demonstrated the effect of micro-solvation on the binding interaction between the metal ions (Cs⁺ and Sr²⁺) and the macrocyclic crown ethers by considering micro-solvated metal ions up to eight water molecules directly attached to the metal ion and also by considering two water molecules attached to metal-ion-crown ether complexes. A metal ion exchange reaction involving the replacement of strontium ion in metal ion-crown ether complexes with cesium ion contained within a metal ion-water cluster serves as the basis for modeling binding preferences in solution. The calculated O-H stretching frequency of H₂O molecule in micro-solvated metal ion-crown complexes is more red-shifted in comparison to hydrated metal ions. The calculated IR spectra can be compared with an experimental spectrum to determine the presence of micro-solvated metal ion–crown ether complexes in extractant phase.     

Isolation and characterization of a new Mycobacterium austroafricanum strain, IFP 2015, growing on MTBE

A new Mycobacterium austroafricanum strain, IFP 2015, growing on methyl tert-butyl ether (MTBE) as a sole carbon source was isolated from an MTBE-degrading microcosm inoculated with drain water of an MTBE-supplemented gasoline storage tank. M. austroafricanum IFP 2015 was able to grow on tert-butyl formate, tert-butyl alcohol (TBA) and α-hydroxyisobutyrate. 2-Methyl-1,2-propanediol was identified as the TBA oxidation product in M. austroafricanum IFP 2015 and in the previously isolated M. austroafricanum IFP 2012. M. austroafricanum IFP 2015 also degraded ethyl tert-butyl ether more rapidly than M. austroafricanum IFP 2012. Specific primers designed to monitor the presence of M. austroafricanum strains could be used as molecular tools to detect similar strains in MTBE-contaminated environment.