Dynamics of microbial community during bioremediation of phenanthrene and chromium (VI) contaminated soil

IBARROLAZA AGUSTÍN; COPPOTELLI BIBIANA M.; DEL PANNO MARÍA T.; DONATI EDGARDO R.; MORELLI IRMA S.

Viena, Austria

Simposio; 11th International Symposium on Microbial Ecology- ISME 11; 2006

Soils are complex systems with different types of contaminants co-existing in different physical and chemical forms. Despite this, organic contaminants and toxic metals are frequently studied separately and their interaction, impact on microbial community and effect that remediation procedures may have on both, is neglected. Our objective was to examine the combined effect of phenanthrene and Cr(VI) on soil microbial activity and community composition, and their effect on the efficiency of bioremediation processes. Soil microcosms contaminated with 2000 mg of phenanthrene per Kg of dry soil and different Cr(VI) concentrations (0, 25, 50 and 100 mg kg -1) were studied. Temperature, soil moisture and oxygen availability were controlled to support bioremediation. Periodically phenanthrene concentration (GC-FID), the number of culturable heterotrophic bacteria (R2A-agar), PAH degrading bacteria (MPN) and biological activity (CO2 production by biometer flask and dehydrogenase activity) were determined.  Physiological profiles of the microbial communities were analyzed using BIOLOG® ECOplate and genetic diversity using PCR-DGGE. The Cr(VI) provoked a decrease in the phenanthrene elimination rate, bacterial populations counts and biological activity, compared with microcosm without Cr(VI). But interestingly, these changes did not show a correlation with Cr(VI) concentration, and more than this, the F-Cr100 microcosm presented higher elimination rate, cell density and biological activity than the F-Cr25 and F-Cr50 microcosms. Whereas the physiological profiles did not show differences by Cr(VI) contamination, clear differences were found between the DGGE patterns of each microcosm, revealing that the structural composition of the bacterial community was affected by phenanthrene contamination and initial Cr(VI) concentration.