The Fractionation of Chlorine Isotopes by the Aerobic Methylotrophic Bacterium Methylobacterium dichloromethanicum Grown on Dichloromethane

Methylobacterium dichloromethanicum was found to be able to utilize dichloromethane (DCM) as the source of carbon and energy with the production of biomass, CO₂, and HCl. A comparative analysis of the abundances of the major DCM isotopomers ³⁵Cl₂¹²C¹H₂, ³⁵Cl³⁷Cl¹²C¹H₂, and ³⁷Cl₂¹²CH₂1H₂ made it possible to estimate the fractionation of chlorine isotopes during the bacterial metabolism of DCM. The kinetic chlorine isotope effects for ³⁵Cl³⁷Cl¹²C¹H₂ (m/z 86) and ³⁷Cl₂¹²C¹H₂ (m/z 88) relative to ³⁵Cl₂¹²C¹H₂ (m/z 84) were characterized by _86/84 = 1.006 ± 0.002 and _88/84 = 1.023 ± 0.003, respectively. The inference is made that the growth of M. dichloromethanicum on DCM is accompanied by the mass-independent fractionation of the DCM isotopomers.