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Applied and Environmental Microbiology, November 1999, p. 5035-5041, Vol. 65, No. 11
U.S. Geological Survey, Menlo Park,
California 94025
Received 4 May 1999/Accepted 27 August 1999
Washed cell suspensions of the facultative methylotroph strain
IMB-1 grown on methyl bromide (MeBr) were able to consume methyl chloride (MeCl) and methyl iodide (MeI) as well as MeBr. Consumption of
>100 µM MeBr by cells grown on glucose, acetate, or monomethylamine required induction. Induction was inhibited by chloramphenicol. However, cells had a constitutive ability to consume low concentrations (<20 nM) of MeBr. Glucose-grown cells were able to readily oxidize [14C]formaldehyde to 14CO2 but
had only a small capacity for oxidation of [14C]methanol.
Preincubation of cells with MeBr did not affect either activity, but
MeBr-induced cells had a greater capacity for [14C]MeBr
oxidation than did cells without preincubation. Consumption of MeBr was
inhibited by MeI, and MeCl consumption was inhibited by MeBr. No
inhibition of MeBr consumption occurred with methyl fluoride, propyl
iodide, dibromomethane, dichloromethane, or difluoromethane, and in
addition cells did not oxidize any of these compounds. Cells displayed
Michaelis-Menten kinetics for the various methyl halides, with apparent
Ks values of 190, 280, and 6,100 nM for MeBr,
MeI, and MeCl, respectively. These results suggest the presence of a
single oxidation enzyme system specific for methyl halides (other than
methyl fluoride) which runs through formaldehyde to CO2.
The ease of induction of methyl halide oxidation in strain IMB-1 should
facilitate its mass culture for the purpose of reducing MeBr emissions
to the atmosphere from fumigated soils.
0099-2240/99/$04.00+0
Oxidation of Methyl Halides by the Facultative
Methylotroph Strain IMB-1
*
Corresponding author. Mailing address: U.S. Geological
Survey, 345 Middlefield Road, MS 480, Menlo Park, CA 94025. Phone: (650) 329-4482. Fax: (650) 329-4463. E-mail:
roremlan{at}usgs.gov.
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