CONICET | Buscador de Institutos y Recursos Humanos

Oil´s contaminated sites are stressful environments for the microorganisms. We hypothesized that some features that increase microbial survival in these environments such as biofilms formation capability or physiological characteristics like reserve substances accumulation (i.e. polyhydroxyalkanoates (PHAs)), could provide to the bacteria some advantages to cope with the environmental stress. We used three polyhydroxyalkanoate producers: Pseudomonas sp. KA-08, isolated from a contaminated sludge, and the Antarctic strains P. extremaustralis and P. extremaustralis/ pGEc4 (transformed with a plasmid containing alk genes) to analyze the effect of PHA accumulation in the hydrocarbon degradation under both planktonic and biofilm growth condition. Two types of bacterial inocula- with or without PHA accumulation- were used. Static biofilm in microtiter plates or planktonic cultures in shaken flasks were assayed. Diesel was selected as pollutant to be tested due to its ubiquity in natural environments. One of the hydrocarbon bioremediation problems is the hydrophobic nature of this pollutant that can be solved by the biosurfactant production ability of microorganisms. To analyze the presence of biosurfactants, free cell supernatants were tested by the "drop collapse" assay. The putative surfactants were pre-purified and the chemical nature of the compounds was analyzed by TLC. Diesel degradation was analyzed by GC. Surfactant production and diesel degradation were considerably higher in all strains when PHA was accumulated. Pseudomonas sp. KA-08 showed enhanced oil degradation compared with P. extremaustralis in both biofilm and planktonic state. Bacteria attached to solid surface (biofilms) were more efficient in diesel degradation than planktonic ones. These results could be useful for environmental biotechnology purposes by analyzing relevant bacterial characteristics to optimize remediation of hydrocarbon contaminated sites

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