Functional characterization of a novel hydrocarbonoclastic Pseudomonas sp. strain PUP6 with plant-growth-promoting traits and antifungal potential

A novel hydrocarbonoclastic bacterium was isolated from rice rhizospheric soil using an enrichment culture technique. Detailed taxonomic studies identified the organism, designated strain PUP6, as a member of the genus Pseudomonas. The bacterium grew in minimal medium amended with n-alkane members of hydrocarbons, n-dodecane (C12H26), n-hexadecane (C16H34), n-octadecane (C18H38), n-octacosane (C28H58); and petroleum fractions such as crude oil and lubricating oil when provided as sole carbon and energy source. Degradation of these n-alkane hydrocarbons and oils in minimal salts medium by strain PUP6 was estimated using gas chromatography with a flame ionization detector. In addition to its hydrocarbonoclastic properties, this bacterium exhibits a broad spectrum of fungal antibiosis against various phytopathogenic fungi. An antifungal metabolite produced by strain PUP6 was isolated, characterized and identified as phenazine-1-carboxamide on the basis of nuclear magnetic resonance and mass spectroscopic analyses. Strain PUP6 also produced plant-growth-promoting siderophores, indoleacetic acid (IAA), phosphate solubilizing enzymes, and fungal cell wall degrading enzymes such as protease and chitinase. This study can be considered as the first report on n-alkane hydrocarbon and oil degradation by a rhizosphere soil bacterium that exhibits biofertilizing and biocontrol traits. Due to its innate multiple functional traits beyond its role in degradation of hydrocarbons, strain PUP6 may be used as plant-growth-promoting rhizobacterium and biocontrol agent against phytopathogenic fungi.