RESUMEN
Lindane (γ-Hexachlorocyclohexane) has been used extensively as a pesticide all over the world. The production of Lindane entails the formation of four major Hexachlorocyclohexane (HCH) isomers, that is, alpha, beta, gamma, and delta as muck. These have been used as Technical HCH in developing countries as an inexpensive alternate source. However, HCH isomers pose a severe environmental hazard due to their highly persistent nature and toxicity. In this study, the effect of HCH application on the soil microbial diversity was studied. The species which could persist even after prolonged exposure at high HCH concentration, was isolated, screened, and enriched as potential t-HCH degraders. The selected isolate could degrade 88.05%, 92.19%, 91.54%, and 82.85% of the alpha, gamma, beta, and delta isomers, respectively at 100 mg/L HCH concentration. Identification of the isolate by 16s rRNA sequencing was similar to Cupriavidus malaysiensis. To the best of the authors' knowledge, this is the first study to observe this particular strain's ability to simultaneously degrade the four isomers, especially the most recalcitrant beta isomer. Therefore, the degradative capability of this strain, as a sole carbon source at higher HCH concentration (100 mg/l), can be exploited for bioremediation of HCH contaminated sites.
Asunto(s)
Cupriavidus , Hexaclorociclohexano , Biodegradación Ambiental , Cupriavidus/genética , Cupriavidus/metabolismo , Hexaclorociclohexano/metabolismo , ARN Ribosómico 16S/genética , SueloRESUMEN
The genotoxic potential of hexachlorocyclohexane (HCH) isomers (α-, ß-, and γ-) which are organochlorine pesticides was tested in peripheral blood lymphocyte cultures from two donors by using the cytokinesis-block micronucleus assay. Micronucleus (MN) frequency, binucleated cells with micronucleus (BNMN), and cytokinesis-blocked proliferation index (CBPI) were determined as genotoxic and cytotoxic endpoints. At the concentration ranges tested (12.5-100 µg.L -1), all HCH isomers induced dose-dependent cytotoxic effects, γ-HCH being the most toxic. This isomer was also able to induce significant increase in MN frequency and BNMN cells indicating a genotoxic potential at 50 and 100 µg.L -1. The genotoxic test of ß-HCH showed a positive induction of MN and BNMN cells at the highest concentration of 100 µg.L -1 and a significant cytotoxicity at 50 µg.L -1. Under the experimental condition used, α-HCH was unable to induce any significant increase in MN frequency confirming that α-HCH is a non-genotoxic agent.
Asunto(s)
Citocinesis/efectos de los fármacos , Hexaclorociclohexano/toxicidad , Linfocitos/efectos de los fármacos , Micronúcleos con Defecto Cromosómico/inducido químicamente , Plaguicidas/toxicidad , Adulto , Técnicas de Cultivo de Célula , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Relación Dosis-Respuesta a Droga , Femenino , Hexaclorociclohexano/química , Humanos , Isomerismo , Linfocitos/patología , Pruebas de Micronúcleos/métodos , Plaguicidas/química , Relación Estructura-ActividadRESUMEN
The organochlorine insecticide γ-hexachlorocyclohexane (γ-HCH, lindane) and its non-insecticidal α- and ß-isomers continue to pose serious environmental and health concerns, although their use has been restricted or completely banned for decades. In this study we report the first evidence of the growth ability of a Streptomyces strain in a mineral salt medium containing high doses of α- and ß-HCH (16.6 mg l(-1)) as a carbon source. Degradation of HCH isomers by Streptomyces sp. M7 was investigated after 1, 4, and 7 days of incubation, determining chloride ion release, and residues in the supernatants by GC with µECD detection. The results show that both the α- and ß-HCH isomers were effectively metabolized by Streptomyces sp. M7, with 80 and 78 % degradation respectively, after 7 days of incubation. Moreover, pentachlorocyclohexenes and tetrachlorocyclohexenes were detected as metabolites. In addition, the formation of possible persistent compounds such as chlorobenzenes and chlorophenols were studied by GC-MS, while no phenolic compounds were detected. In conclusion, we have demonstrated for the first time that Streptomyces sp. M7 can degrade α- and ß-isomers individually or combined with γ-HCH and could be considered as a potential agent for bioremediation of environments contaminated by organochlorine isomers.