RESUMO
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.
Assuntos
Hexaclorocicloexano/química , Hexaclorocicloexano/metabolismo , Poluentes do Solo/química , Poluentes do Solo/metabolismo , Streptomyces/metabolismo , Anaerobiose , Biodegradação Ambiental , Inseticidas/química , Inseticidas/metabolismo , IsomerismoRESUMO
This work was conducted to study the removal of gamma-hexachlorocyclohexane (lindane) in a soil extract liquid medium (SE) by Streptomyces sp. M7 and to determine the influence of pH and temperature on bacterial growth and pesticide removal in this medium. When Streptomyces sp. M7 was cultured in SE supplemented with lindane 100 microg l(-1 )at different initial pH, the maximum growth was observed at pH 7 and the microorganism was not able to grow at pH 5 and 9; the highest pesticide removal (70.4%) by Streptomyces sp. M7 was noted at an initial pH of 7 at 4 weeks of incubation. The maximum removal (70% approximately) was observed when the microorganism was incubated in SE at 30 degrees C; although the optimal temperature for Streptomyces sp. M7 growth, with and without lindane, was 25 degrees C, and for the pesticide removal was 30 degrees C. The results of this study suggest that this actinomycete strain appears as an effective alternative in the remediation of lindane polluted sites.
Assuntos
Hexaclorocicloexano/metabolismo , Streptomyces/metabolismo , Biodegradação Ambiental , Misturas Complexas , Concentração de Íons de Hidrogênio , Solo , Microbiologia do Solo , Streptomyces/crescimento & desenvolvimento , TemperaturaRESUMO
Gamma-hexachlorocyclohexane (gamma-HCH or lindane), one of the most commonly used pesticides, has been mainly used in agriculture; this pesticide is known to be highly toxic and persistent, causing serious water and soil contamination. The objective of the present work is to study the effect of low glucose concentration and the addition of lindane at different growing time on the pesticide detoxification ability of Streptomyces M7. After 96 h of incubation in synthetic medium containing glucose 0.6 g l(-1) with the addition of lindane 100 microg l(-1) at 20 h of incubation, a typical diauxic curve was obtained: glucose was the preferred substrate until 24 h, at 48 h, when the carbohydrate was depleted, the microorganism consumed the pesticide like carbon source. On the other hand, lindane removal induction was observed, which was greater when the pesticide was added to the medium at 20 h than 6 h of incubation. Between 72 and 96 h, a maximum of approximately 86% of the Cl(-) was released when lindane was added to the medium at 20 h, whereas approximately 70% and 67% Cl(-) was released in the medium when the pesticide was added at 0 and 6 h of incubation respectively. This is the first report of chloride release from inoculated medium supplemented with lindane, suggesting that the pesticide was degraded by Streptomyces sp. under aerobic conditions.
Assuntos
Hexaclorocicloexano/metabolismo , Inseticidas/metabolismo , Streptomyces/metabolismo , Biodegradação Ambiental , Cloretos/metabolismo , Meios de Cultura , Ecossistema , Sedimentos Geológicos/microbiologia , Glucose/metabolismo , Streptomyces/crescimento & desenvolvimento , Streptomyces/isolamento & purificaçãoRESUMO
Ninety-three wild-type isolates identified as actinomycetes were tested against 11 organochlorine pesticides (OPs): aldrin, chlordane, DDD, DDE, DDT, dieldrin, heptachlor, and heptachlor epoxides, lindane, and methoxychlor. Qualitative screening agar assays displayed 62-78% tolerance of strains to OPs. Four strains designed M4, M7, M9 and M15 were selected based on multi-OP-tolerance, and identified as members of the streptomycetes group. Different growth profiles were observed in cultures of the four selected streptomycetes cultured in synthetic medium containing 5-50 microg x l(-1) aldrin or chlordane or lindane. Increase of aldrin removal by the selected microorganisms was concomitant with the 4.8-36.0 microg x l(-1) pesticide concentration range. After 72 h of streptomycete M7 growth in synthetic medium containing 48.0 microg x l(-1) aldrin, the remaining OP concentration in the supernatant was approximately 10% of the initial concentration. Also, in stationary growth phase less than 2.5 microg x l(-1) aldrin residual concentration was detected in the medium.