Dechlorination activity detection in Streptomyces sp. M7

S.A. CUOZZO,; C.N.CHAVARRÍA,; G.C. ROLLÁN,; C.M. ABATE; AND M.J. AMOROSO

Dalian, China

Simposio; Thirteenth International Biotechnology Symposium & Exhibition; 2008

The lindane (gamma-hexachlorocyclohexane) is a lyphophilic compound, and therefore tends to accumulate and concentrate in the body fat of the man [3] and it is one of the major problems facing the industrialized world. Lindane is considered a potential carcinogen and it is listed as priority pollutant by the US EPA [4]. Little information is available on the ability of organochlorine pesticide biotransformation by Gram-positive microorganisms and particularly by actinomycete species, the main group of bacteria present in soils and sediments [5]. However an indigenous isolated M7 strain demonstrated that it can grow in the lindane presence as only carbon sources [6]. The ability of actinomycetes to transform organochlorine pesticides has not been widely investigated, metabolic pathways for pesticide biodegradation by Gram negative bacteria have been more extensively studied than in Gram-positive as the case of an aerobic degradation way of lindane Sphingobium japonicum where the first step is the dehalogenase activity to obtain pentachloride+cyclohexane+pentachlorocyclohexene. The aim of this work is to determine if Streptomyces M7 possess the dehalogenase activity because so far there is no any information. Dehalogenase activity was measured using free-cell extract from Streptomyces cultured in flasks containing 30 ml liquid minimal medium supplemented with and without lindane 10 mg/1, on a rotatory shaker (100 rpm) at 30 ºC, for 96 h. Samples were taken at 96 h and centrifuged (9,900 g., 10 min), the cells were broken by the French Press and centrifuged. The supernatant was used by detecting the dechlorination reaction. The dechlorination activity was measured by spectrophotometer at 595 nm [8]. Optimal temperature, pH and Ca concentration were determined for optimizing the dechlorinase activity. The obtained results show that Streptomyces M7 presents intracellular dechlorinase activity. It is also four-times more than the control. On the other hand the best conditions for the dechlorinase activity are 30 ºC , alkaline pH (9.5) and the presence of calcium cation at 0.5 mM final concentration. These results show for the first time the presence of the dechlorinase activity in an actinomycete strain. The knowledge of the best conditions for maximal activity is of great importance by the future in facing the biorremediation improvement in lindane contaminated environment. , M.J., del Hidalgo, M.V., Apella, M.C., 1999. Organochlorine pesticides in Sali River. Tucumán?Argentina (In Spanish). Revista Boliviana de Ecología 6, 203?209. [2]Botella, B., Crespo, J., Rivas, A., Cerrillo, I., Olea-Serrano, M.F., Olea, N., 2004. Exposure of women to organochlorine pesticides in Southern Spain. Environmental Research 96, 34?40. [3]Johri, A.K., Dua, M., Saxena, D.M., Sethunathan, N., 2000. Enhanced degradation of hexachlorocyclohexane isomers by Sphingomonas paucimobilis. Current Microbiology 41, 309?311. [4]Walker, K., Vallero, D.A. and Lewis, R.G., 1999. Factors influencing the distribution of lindane and other hexachlorocyclohexanes in the environment. Environ. Sci. Technol., 33, 4373?4378. [5]De Schrijver, A., De Mot, R., 1999. Degradation of pesticides by actinomycetes. Critical Reviews in Microbiology 25, 85?119. [6]Benimelia, C.S., Fuentesa, M.S., Abatea, C.M.,  Amoroso, M.J. 2008 Bioremediation of lindane-contaminated soil by Streptomyces sp. M7 and its effects on Zea mays growth. International Biodeterioration & Biodegradation. In press [7] Nagata Y., Endo R., Ito M., Ohtsubo Y., Tsuda M. 2007 Aerobic degradation of lindane (gamma-hexachlorocyclohexane) in bacteria and its biochemical and molecular basis. Appl. Microbiol. Biotechnol. 76, 741-52. [8]Phillips, T.M., Seech, A.G., Lee, H., Trevors, J.T.,2001. Colorimetric assay for lindane dechlorination by bacteria. Journal of Microbiological Methods 47, 181?188.