Note Bacterial degradation of dichloromethane in cultures and natural environments Valentina I. Krausova a,b , Frank T. Robb b , Juan M. Gonza ´lez b,c, * a Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia b Center of Marine Biotechnology, 701 E. Pratt Street, Baltimore, MD 21202, USA c Instituto de Recursos Naturales y Agrobiologı ´a, CSIC, P.O. Box 1052, 41080 Seville, Spain Received 4 October 2002; received in revised form 28 January 2003; accepted 11 February 2003 Abstract Dichloromethane (DCM) is a toxic pollutant showing prolonged persistence in water. DCM biodegradation is usually determined from increases in Cl ions, gas chromatography, or by using radioisotopes. Herein, we present an original and easy spectrophotometric method to estimate DCM concentrations in cultures and environmental samples during DCM biodegradation experiments. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Dichloromethane; Biodegradation; Dichloromethane dehalogenase; Enzyme assay Dichloromethane (DCM) is a highly toxic com- pound widely used as an industrial solvent. DCM has been in widespread use for several decades, with the principal application being paint removal (U.S. International Trade Commission, 1970 – 1985). It has been shown to cause lung and liver cancer in rodents (National Toxicology Program, 1986), and a number of harmful effects on humans have been reported (Edwards et al., 1982; Dhillon and Von Burg, 1995). DCM is difficult to remove from contaminated waters (Mackay and Cherry, 1989) and shows high persistence in water (half-life over 700 years) and atmosphere (half-life 79 days). Thus, there is a growing interest in studying biodegradative pro- cesses of DCM in natural environments (Edwards et al., 1982; Ga ¨lli and Leisinger, 1985; Freedman and Gossett, 1991). Currently, DCM concentration is determined mainly by capillary gas chromatography (Oldenhuis et al., 1989), and DCM dehalogenase activity has been assessed from the dehalogenation of DCM (Brunner et al., 1980), by enzymatic assays (Leisinger and Kohler-Staub, 1990; Bader and Leisinger, 1994), or by using radioisotopes (Goodwin et al., 1998). Capillary gas chromatography is a sensitive method to estimate a concentration of DCM in a sample; however, it requires relatively costly equipment un- available to many microbiologists. There are a number of techniques for assessing DCM dehalogenase activ- ity. Continuous monitoring of the acid produced during the dehalogenation of DCM is a simple method 0167-7012/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0167-7012(03)00062-9 * Corresponding author. Instituto de Recursos Naturales y Agrobiologı ´a, CSIC, P.O. Box 1052, 41080 Seville, Spain. Tel.: +34-95-462-4711; fax: +34-95-462-4002. E-mail address: jmgrau@irnase.csic.es (J.M. Gonza ´lez). www.elsevier.com/locate/jmicmeth Journal of Microbiological Methods 54 (2003) 419 – 422