RESUMO
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.
Assuntos
Hidrocarbonetos Clorados , Inseticidas/metabolismo , Streptomycetaceae/fisiologia , Purificação da Água/métodos , Biodegradação Ambiental , Streptomycetaceae/isolamento & purificaçãoRESUMO
Streptomycetes constituted about 46--48 per cent of the total aerobic microflora in the cultivated horizon of the studied ferralitic tropical soil below sugar cane plantation. This streptomycete fraction of the soil microbial community was composed of 13 (or more) species of Streptomyces (S. chromofuscus, S. chromogenus, S. diastatochromogenes, S. flavochromogenes, S. griseolus, S. nigrescens, S. phaeofaciens, S. sterilis, S. violaceus, Streptomyces sp. I--III), and Streptoverticillium (Sv. aspergilloides). None of these organisms did occur, with detectable frequency of occurrence, in the root surface region of sugar cane. Here, in the rhizoplane, we found a numerically small population of streptomycetes (about 5 per cent of the total bacterial flora), composed of two species (Streptomyces sp. IV and S. griseorubiginosus) which were, however, not detected in soil samples.