RESUMEN
The insecticide chlordecone is a contaminant found in most of the banana plantations in the French West Indies. This study aims to search for fungal populations able to grow on it. An Andosol heavily contaminated with chlordecone, perfused for 1 year in a soil-charcoal system, was used to conduct enrichment cultures. A total of 103 fungal strains able to grow on chlordecone-mineral salt medium were isolated, purified, and deposited in the MIAE collection (Microorganismes d'Intérêt Agro-Environnemental, UMR Agroécologie, Institut National de la Recherche Agronomique, Dijon, France). Internal transcribed spacer sequencing revealed that all isolated strains belonged to the Ascomycota phylum and gathered in 11 genera: Metacordyceps, Cordyceps, Pochonia, Acremonium, Fusarium, Paecilomyces, Ophiocordyceps, Purpureocillium, Bionectria, Penicillium, and Aspergillus. Among predominant species, only one isolate, Fusarium oxysporum MIAE01197, was able to grow in a liquid culture medium that contained chlordecone as sole carbon source. Chlordecone increased F. oxysporum MIAE01197 growth rate, attesting for its tolerance to this organochlorine. Moreover, F. oxysporum MIAE01197 exhibited a higher EC50 value than the reference strain F. oxysporum MIAE00047. This further suggests its adaptation to chlordecone tolerance up to 29.2 mg l(-1). Gas chromatography-mass spectrometry (GC-MS) analysis revealed that 40 % of chlordecone was dissipated in F. oxysporum MIAE01197 suspension culture. No chlordecone metabolite was detected by GC-MS. However, weak amount of (14)CO2 evolved from (14)C10-chlordecone and (14)C10-metabolites were observed. Sorption of (14)C10-chlordecone onto fungal biomass followed a linear relationship (r (2) = 0.99) suggesting that it may also account for chlordecone dissipation in F. oxysporum MIAE01197 culture.
Asunto(s)
Clordecona/toxicidad , Farmacorresistencia Fúngica/genética , Hongos/fisiología , Insecticidas/toxicidad , Contaminantes del Suelo/toxicidad , Secuencia de Bases , Biomasa , Clordecona/análisis , Hongos/aislamiento & purificación , Insecticidas/análisis , Datos de Secuencia Molecular , Musa , Suelo/química , Microbiología del Suelo , Contaminantes del Suelo/análisis , Indias OccidentalesRESUMEN
PURPOSE: Evidence has accumulated that humic substances (HS) are not inert biogeochemicals. Rather, they cause stress symptoms and may modulate the life history of aquatic organisms. Nevertheless, it is still not clear how HS interact with additional stressors and if their effects are transgenerational. We tested the interactive effects of HS and salt to cladocerans, discussing their consequences for the persistence in fluctuating environments, such as coastal lagoons. METHODS: We used life-table experiments to test the effects of natural HS from a polyhumic coastal lagoon (0, 5, 10, 20, 50, and 100 mg dissolved organic carbon (DOC) L(-1)) on the life-history of the cladoceran Moina macrocopa. We further tested the effects of HS (10 mg DOC L(-1)), within and across generations, on the resistance of M. macrocopa to salt stress (5.5 g L(-1)). RESULTS: HS at 5-20 mg DOC L(-1) extended the mean lifespan of M. macrocopa by ~30%. HS also increased body length at maturity by ~4% at 5-50 mg DOC L(-1) and stimulated male offspring production at all tested concentrations. Exposure to HS (even maternal only) alleviated the salt-induced reduction of somatic growth. Co-exposure to HS increased body volume by 12-22% relative to salt-only treatments, while pre-exposure to HS increased body volume by 40-56% in treatments with salt presence, when compared to non-pre-exposed animals. CONCLUSIONS: HS at environmentally realistic concentrations, by acting as mild chemical stressors, modify crucial life-history traits of M. macrocopa, favoring its persistence in fluctuating environments. Some of the effects of HS are even transgenerational.