US EPA

4140400 

Journal Article 

Dichloromethane as the sole carbon source for an acetogenic mixed culture and isolation of a fermentative, dichloromethane-degrading bacterium 

Braus-Stromeyer, SA; Hermann, R; Cook, AM; Leisinger, T 

1993 

No 

Applied and Environmental Microbiology
ISSN: 0099-2240
EISSN: 1098-5336 

59 

11 

3790-3797 

English 

8285685 

WOS:A1993ME66000041 

http://aem.asm.org/content/59/11/3790.abstract
Exit
 

Dichloromethane (DCM) is utilized by the strictly anaerobic, acetogenic mixed culture DM as a sole source of carbon and energy for growth. Growth with DCM was linear, and cell suspensions of the culture degraded DCM with a specific activity of 0.47 mkat/kg of protein. A mass balance of 2 mol of chloride and 0.42 mol of acetate per mol of DCM was observed. The dehalogenation reaction showed similar specific activities under both anaerobic and aerobic conditions. Radioactivity from [14C]DCM in cell suspensions was recovered largely as 14CO2 (58%), [14C]acetate (23%), and [14C]formate (11%), which subsequently disappeared. This suggested that formate is a major intermediate in the pathway from DCM to acetate. Efforts to isolate from culture DM a pure culture capable of anaerobic growth with DCM were unsuccessful, although overall acetogenesis and the partial reactions are thermodynamically favorable. We then isolated bacterial strains DMA, a strictly anaerobic, gram-positive, endospore-forming rod, and DMB, a strictly anaerobic, gram-negative, endospore-forming homoacetogen, from culture DM. Both strain DMB and Methanospirillum hungatei utilized formate as a source of carbon and energy. Coculture of strain DMA with either M. hungatei or strain DMB in solid medium with DCM as the sole added source of carbon and energy was observed. These data support a tentative scheme for the acetogenic fermentation of DCM involving interspecies formate transfer from strain DMA to the acetogenic bacterium DMB or to the methanogen M. hungatei.