Degradation of 1,4-Dioxane and Cyclic Ethers by an Isolated Fungus

The filamentous fungus Graphium sp. (ATCC 58400) grows on gaseous n-alkanes and diethyl ether. nAlkane-grown mycelia of this strain also cometabolically oxidize the gasoline oxygenate methyl tert-butyl ether (MTBE). In this study, we characterized the ability of this fungus to metabolize and cometabolize a range of cyclic ethers, including tetrahydrofuran (THF) and 1,4-dioxane (14D). This strain grew on THF and other cyclic ethers, including tetrahydropyran and hexamethylene oxide. However, more vigorous growth was consistently observed on the lactones and terminal diols potentially derived from these ethers. Unlike the case in all previous studies of microbial THF oxidation, a metabolite, ␥-butyrolactone, was observed during growth of this fungus on THF. Growth on THF was inhibited by the same n-alkenes and n-alkynes that inhibit growth of this fungus on n-alkanes, while growth on ␥-butyrolactone or succinate was unaffected by these inhibitors. Propane and THF also behaved as mutually competitive substrates, and propane-grown mycelia immediately oxidized THF, without a lag phase. Mycelia grown on propane or THF exhibited comparable high levels of hemiacetal-oxidizing activity that generated methyl formate from mixtures of formaldehyde and methanol. Collectively, these observations suggest that THF and n-alkanes may initially be oxidized by the same monooxygenase and that further transformation of THF-derived metabolites involves the activity of one or more alcohol dehydrogenases. Both propane-and THF-grown mycelia also slowly cometabolically oxidized 14D, although unlike THF oxidation, this reaction was not sustainable. Specific rates of THF, 14D, and MTBE degradation were very similar in THF-and propane-grown mycelia.

mentioning

confidence: 99%

Metabolism and Cometabolism of Cyclic Ethers by a Filamentous Fungus, aGraphiumsp

Skinner

Cuiffetti

Hyman

2009

“…A number of pure and mixed cultures of bacteria and fungi have been reported to degrade dioxane aerobically (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), while only one study has reported anaerobic degradation (13). To date, nine microorganisms have been reported to be capable of growth on dioxane as a sole carbon and energy source (i.e., metabolism of dioxane), including Rhodococcus ruber 219 (1), Mycobacterium sp.…”

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confidence: 99%

“…To date, nine microorganisms have been reported to be capable of growth on dioxane as a sole carbon and energy source (i.e., metabolism of dioxane), including Rhodococcus ruber 219 (1), Mycobacterium sp. strain PH-06 (12), Pseudonocardia dioxanivorans CB1190 (3,14), Pseudonocardia benzenivorans B5 (11), the fungus Cordyceps sinensis (9), and four recently isolated strains identified as two Mycobacterium spp., a Pseudonocardia sp., and a Gram-negative Afipia sp. (15).…”

mentioning

confidence: 99%

Oxidation of the Cyclic Ethers 1,4-Dioxane and Tetrahydrofuran by a Monooxygenase in Two Pseudonocardia Species

Sales

Grostern

Parales

et al. 2013

The bacterium Pseudonocardia dioxanivorans CB1190 grows on the cyclic ethers 1,4-dioxane (dioxane) and tetrahydrofuran (THF) as sole carbon and energy sources. Prior transcriptional studies indicated that an annotated THF monooxygenase (THF MO) gene cluster, thmADBC, located on a plasmid in CB1190 is upregulated during growth on dioxane. In this work, transcriptional analysis demonstrates that upregulation of thmADBC occurs during growth on the dioxane metabolite ␤-hydroxyethoxyacetic acid (HEAA) and on THF. Comparison of the transcriptomes of CB1190 grown on THF and succinate (an intermediate of THF degradation) permitted the identification of other genes involved in THF metabolism. Dioxane and THF oxidation activity of the THF MO was verified in Rhodococcus jostii RHA1 cells heterologously expressing the CB1190 thmADBC gene cluster. Interestingly, these thmADBC expression clones accumulated HEAA as a dead-end product of dioxane transformation, indicating that despite its genes being transcriptionally upregulated during growth on HEAA, the THF MO enzyme is not responsible for degradation of HEAA in CB1190. Similar activities were also observed in RHA1 cells heterologously expressing the thmADBC gene cluster from Pseudonocardia tetrahydrofuranoxydans K1.

“…Metabolic degradation is less common, with only a few microorganisms being able to use dioxane as the sole source for carbon and energy (18,(30)(31)(32). Cometabolic pathways include several monooxygenase enzymes required for dioxane degradation, including the methane (MMO), propane (PrMO), phenol (PHE), tetrahydrofuran (THFMO), and toluene (TOL, T4MO, or RMO), monooxygenases (19,20,28,33,34).…”

mentioning

confidence: 99%

Identification of Biomarker Genes To Predict Biodegradation of 1,4-Dioxane

Gedalanga

Pornwongthong

Mora³

et al. 2014

Bacterial multicomponent monooxygenase gene targets in Pseudonocardia dioxanivorans CB1190 were evaluated for their use as biomarkers to identify the potential for 1,4-dioxane biodegradation in pure cultures and environmental samples. Our studies using laboratory pure cultures and industrial activated sludge samples suggest that the presence of genes associated with dioxane monooxygenase, propane monooxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase are promising indicators of 1,4-dioxane biotransformation; however, gene abundance was insufficient to predict actual biodegradation. A time course gene expression analysis of dioxane and propane monooxygenases in Pseudonocardia dioxanivorans CB1190 and mixed communities in wastewater samples revealed important associations with the rates of 1,4-dioxane removal. In addition, transcripts of alcohol dehydrogenase and aldehyde dehydrogenase genes were upregulated during biodegradation, although only the aldehyde dehydrogenase was significantly correlated with 1,4-dioxane concentrations. Expression of the propane monooxygenase demonstrated a time-dependent relationship with 1,4-dioxane biodegradation in P. dioxanivorans CB1190, with increased expression occurring after over 50% of the 1,4-dioxane had been removed. While the fraction of P. dioxanivorans CB1190-like bacteria among the total bacterial population significantly increased with decrease in 1,4-dioxane concentrations in wastewater treatment samples undergoing active biodegradation, the abundance and expression of monooxygenase-based biomarkers were better predictors of 1,4-dioxane degradation than taxonomic 16S rRNA genes. This study illustrates that specific bacterial monooxygenase and dehydrogenase gene targets together can serve as effective biomarkers for 1,4-dioxane biodegradation in the environment.