Antifungal activity and plant growth promotion characteristics of hydrocarbon degrading Pseudomonas aeruginosa and Enterobacter sp. Isolated from polluted soil

Diesel oil is a complex mixture of aliphatic and aromatic hydrocarbons, which due to the wide usage has become a frequent environmental pollutant. Then, it is imperative to explore viable and economic alternatives for diesel oil degradation. The purpose of this work was to analyze the degradation of diesel oil by bacteria isolated from polluted soil, as well as to evaluate the antagonistic activity against phytopathogenic fungi, the plant growth promotion characteristics, and metal tolerance. From the enrichment in diesel oil as carbon source the J3 and S3 bacterial isolates were obtained, the biochemical and molecular identification indicates that these isolates were Pseudomonas aeruginosa and Enterobacter sp., respectively. Furthermore, the bacterial growth between 2 and 5 % of diesel oil was better, whereas the optimal pH was of 7.0 and 8.0 in the presence of 3 % of diesel oil, also, S3 showed growth at concentration of 4 % of NaCl. Even more, both bacteria showed inhibition of the phytopathogenic fungi Alternaria sp., Botrytis cinerea, Colletotrichum siamense and Fusarium proliferatum and plant growth promoting traits as indoleacetic acid (IAA) production, phosphate solubilization, siderophores and surfactant production. Also, bacterial growth was observed specially for Zn, Cu, Ba, and Pb, in concentrations between 1.5 and >10 mM. In conclusion, the bacteria identified in this study presented characteristics that made them good candidates for the remotion of hydrocarbons alone or by phytoremediation due to its characteristics of plant growth promotion.