title: Metabolism of 2-methylpropene (isobutylene) by the aerobic bacterium Mycobacterium sp. strain ELW1.
abstract: An aerobic bacterium (Mycobacterium sp. strain ELW1) that utilizes 2-methylpropene (isobutylene) as a sole source of carbon and energy was isolated and characterized. Strain ELW1 grew on 2-methylpropene (growth rate = 0.05 h(-1)) with a yield of 0.38 mg (dry weight) mg 2-methylpropene(-1). Strain ELW1 also grew more slowly on both cis- and trans-2-butene but did not grow on any other C2 to C5 straight-chain, branched, or chlorinated alkenes tested. Resting 2-methylpropene-grown cells consumed ethene, propene, and 1-butene without a lag phase. Epoxyethane accumulated as the only detected product of ethene oxidation. Both alkene consumption and epoxyethane production were fully inhibited in cells exposed to 1-octyne, suggesting that alkene oxidation is initiated by an alkyne-sensitive, epoxide-generating monooxygenase. Kinetic analyses indicated that 1,2-epoxy-2-methylpropane is rapidly consumed during 2-methylpropene degradation, while 2-methyl-2-propen-1-ol is not a significant metabolite of 2-methylpropene catabolism. Degradation of 1,2-epoxy-2-methylpropane by 2-methylpropene-grown cells led to the accumulation and further degradation of 2-methyl-1,2-propanediol and 2-hydroxyisobutyrate, two sequential metabolites previously identified in the aerobic microbial metabolism of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA). Growth of strain ELW1 on 2-methylpropene, 1,2-epoxy-2-methylpropane, 2-methyl-1,2-propanediol, and 2-hydroxyisobutyrate was fully inhibited when cobalt ions were omitted from the growth medium, while growth on 3-hydroxybutyrate and other substrates was unaffected by the absence of added cobalt ions. Our results suggest that, like aerobic MTBE- and TBA-metabolizing bacteria, strain ELW1 utilizes a cobalt/cobalamin-dependent mutase to transform 2-hydroxyisobutyrate. Our results have been interpreted in terms of their impact on our understanding of the microbial metabolism of alkenes and ether oxygenates.
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Samanthi
authors.initials: S
authors.lastname: Kottegoda
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Waligora
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA mrhyman@ncsu.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Hyman
mesh_terms: D000332:Aerobiosis; D000475:Alkenes / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D003035:Cobalt / Q000378:metabolism; D003067:Coenzymes / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004734:Energy Metabolism; D006885:Hydroxybutyrates / Q000378:metabolism; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000302:isolation & purification / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D000475:Alkenes; D003067:Coenzymes; D003470:Culture Media; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D006885:Hydroxybutyrates; D012336:RNA, Ribosomal, 16S; D003035:Cobalt; D002244:Carbon; C008039:2-hydroxyisobutyric acid; C008176:isobutylene