Pesticides Removal Using Actinomycetes and Plants

ALVAREZ, ANALÍA; FUENTES, M. SOLEDAD; BENIMELI CLAUDIA S.; CUOZZO, SERGIO; SAEZ, JULIANA M.; AMOROSO MARÍA JULIA

Fungi as bioremediators

Springer

Lugar: Tehrán; Año: 2013; p. 227 - 242

The gama-hexachlorocyclohexane (gama-HCH, lindane) is an organochlorine pesticide used in agriculture and medicine to world level. It has a big tendency to bioaccumulation into the environment so is listed as a priority pollutant by the US EPA. 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 pesticide contaminated sediment, was selected for its capacity to grow in presence of lindane as only carbon source. This microorganism was cultured in soil extract medium added of lindane 100 microg L-1, obtaining a maximal growth of 0.065 mg mL1, similar to the control, with a highest lindane remotion of 70.4 percent at 30 ºC and pH 7. When different initial pesticide concentration (100, 150, 200 y 300 microg L-1) was 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 soils samples in relation to controls without bacteria (29.1, 78.0, 38.8 and 14.4 percent, respectively). Besides it was determined the optimum Streptomyces sp. M7 inoculum when lindane 100 microg Kg-1soil was added to the soil sample. It was 2 g Kg-1 soil for obtaining the most efficiently bioremediation process, the lindane removal in these conditions was 67.8 percent 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 percent of lindane was removed. In this connection, Streptomyces sp. M7 was grown on culture medium in presence of root exudates of maize, spiked with 1.66 mg L-1 of lindane. The highest level of pesticide removal obtained on this condition suggests that root exudates enhanced removal of lindane by the bacterium. On the other hand, little information is available on the ability of biotransformation of organochlorine pesticides by actinomycete strains. It was demonstrated that Streptomyces sp. M7 possesses the LinA enzyme that catalyzes dehydrochlorination of lindane to 1,3,4,6-tetrachloro-1,4-cyclohexadiene (1,4-TCDN) via γ-pentachlorocyclohexene (γ-PCCH). These results confirm that actinomycetes strains could be considered one of the most promising bacterial groups for lindane biodegradation in contaminated environment. Particularly, Streptomyces sp. M7 could be used for this purpose.