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ORGANOCHLORINE PESTICIDES BIODEGRADATION BY INDIGENOUS ACTINOMYCETES STRAINS 1,3Benimeli, C.S.; 1Fuentes, M.S.; 1Sáez, J.M.; 1 Bourguignon, N.; 1Cuozzo, S.A.; and 1,2,3Amoroso, M.J. 1PROIMI-CONICET, 2Fac. de Bqca, Qca y Fcia. UNT.3UNSTA. Tucumán, Argentina. cbenimeli@proimi.org.ar Organochlorine pesticides (OPs) have been extensively used to protect and improve quality and quantity of food commodities, building materials, clothing, animal health, and to combat certain diseases transmitted by insect vectors to man and animals. However, indiscriminate use of pesticides has caused serious concern about toxic effects by residues on non-target organisms. The g-HCH is an organochlorine pesticide used in agriculture and medicine to world level. It has a big tendency to bioaccumulate into the environment. There are many reports indicating that hexachlorocyclohexane (g-HCH) is present in soil, water, air, plants, agricultural products, animals, food, microbial environments etc. Considered a potential carcinogen and listed as a priority pollutant by the US EPA, g-HCH is a lipophilic compound and therefore tends to accumulate and concentrate in the body fats of animals and humans. In Salí River, the main hydrographic system of Tucumán, Argentina, lindane was detected 10-fold in relation to the traces permitted concentrations. Hence the development of new technologies to remediate these sites using microorganisms is every time more necessary. The actinomycetes are Gram positive bacteria with great potential to bioremediate xenobiotics. One strain, Streptomyces sp M7, isolated from organochlorine pesticides contaminated sediment was selected for its capacity to grow in the presence of lindane as only carbon source. This microorganism was cultured in soil extract medium added of lindane 100 mg L-1, obtaining a maximal growth of 0.065 mg mL-1, similar to the control, with a highest lindane removal of 70.4% at 30 ºC and pH 7. When different initial pesticide concentrations (100, 150, 200 and 300 mg L-1) were added in soil medium, an increment of the microbial growth was detected in all the concentrations tested. Also a diminution of the residual lindane concentration was determined in the soil samples in relation to the abiotic controls (29.1; 78.03; 38.81 and 14.42% respectively). Besides it was determined the optimum Streptomyces sp. M7 inoculum when lindane 100 mg Kg-1soil was added to the soil sample. It was 2 g Kg-1soil for obtaining the most efficiently bioremediation process, the lindane removal in these conditions was 67.8% at 28 days of incubation. Later it was considered necessary to know the pesticide effects on maize plants seeded in lindane-contaminated soil previously inoculated with Streptomyces sp. M7. Lindane concentrations of 100, 200, and 400 mg kg-1 soil did not affect the germination and vigor index of maize plants seeded in contaminated soils without Streptomyces sp. M7. When this microorganism was inoculated at the same conditions a better vigor index was observed and 68% of lindane was removed. These results confirm the potential lindane-contaminated soil bioremediation of Streptomyces sp. M7. It is important to notice that for the first time the lindane degradation without intracellular accumulation or biotransformation products of lindane using Streptomyces sp. under aerobic conditions was reported. There are some reports regarding aerobic degradation of g-HCH by Gram-negative bacteria like Sphingomonas and by the white-rot fungi Trametes hirsutus, Phanerochaete chrysosporium, Cyathus bulleri and Phanerochaete sordida. However, little information is available on the ability of biotransformation of organochlorine pesticides by Gram positive bacteria and particularly by actinomycete species. It was demonstrated that Streptomyces sp. M7 possesses the LinA enzyme that catalyzes dehydrochlorination of γ-HCH to 1,3,4,6-tetrachloro-1,4-cyclohexadiene (1,4-TCDN) via γ-pentachlorocyclohexene (γ-PCCH). The increase of γ-PCCH was detected in the time by Gas Chromatography (GC-MS). On the other side two actinomycetes defined consortia with lindane biodegradation capacity, were studied. They were prepared using isolated strains from soil samples of an illegal deposit of organochlorine pesticides in the locality of Santiago del Estero, Argentina. These consortia were: Streptomyces sp. A2-A5-M7-A11 and Streptomyces A2-A5-A8. Both produced a significant increment of the specific dechlorinase activity (SDA), compared to the individual culture with 1.66 mg L-1 of lindane as the only carbon source. Therefore actinomycete consortium strains could be considered one of the most promising bacterial groups for lindane biodegradation in contaminated environment. Finally, other organochlorine pesticides (chlordane and metoxichlor) are trying to be degraded using these new isolates of actinomycete strains. Highest growth and pesticide removal were observed when chlordane was added to the culture medium as the only carbon source. Twelve out of 18 studied strains released chloride into culture supernatants, and percentages were higher with chlordane as carbon source than with lindane or methoxychlor. These results were supported by principal component analysis. It is important to notice that for the first time it was demonstrated that actinomycetes isolated from an illegal storage of organochlorine pesticide in Argentina, have capacity to growth, remove and use chlordane or metoxichlor as the only carbon source.