Isolation and characterization of indigenous soil bacteria for bioaugmentation of PAH contaminated soil of semiarid Patagonia, Argentina

The aim of this work was to isolate PAH degrading-bacteria from contaminated Patagonia soil with the ability to tolerate the usual environmental stresses (oligotrophic and dryness conditions). Two approaches were utilized to obtain PAH-degrading bacteria from the Patagonian soil. With a traditional enrichment approach only the PAH- degrading strain 36 was isolated. Using a direct isolation approach three PAH-degrading strains (1A, 22A and 22B) were isolated. The phylogenetic analysis revealed that all isolates belonged to Sphingomonas genus. The PAH degrading activity and the resistance to stress conditions of the strains were determined and compared with those of the exogenous PAH-degrading Sphingomonas paucimobilis 20006FA. The strains 1A, 22A and 36 were phylogenetically closely related between them and with the strain 20006FA. The strain 22B, that showed a different phylogenetic position, was more resistant to C-starvation and drying conditions than other Patagonian strains. The effect of the inoculation of these strains on phenanthrene-induced mineralization and elimination was studied in Patagonian soil artificially contaminated, at different environmental conditions. The results suggest that strain 22B is the most suitable strain for bioaugmentation in PAH-contaminated soils of Central Patagonia, due to its adaptation to the usual environmental conditions. Our results show the importance of a detailed physiological characterization of isolates for autochthonous bioaugmentation strategies success.