EVALUATION OF DUAL ACTIVITY OF BACTERIAL ISOLATES: HYDROCARBON DEGRADATION AND PROMOTION OF PLANT GROWTH, ADVANTAGEOUS FOR SOIL REMEDIATION OF PETROLEUM HYDROCARBON CONTAMINATION

摘要

This study investigated 60 strains isolated from petroleum hydrocarbons (PHC) contaminated soils from urban and semi-urban areas by providing motor oil or diesel oil or n- hexadecane as a source of carbon and energy. Based on the growth response of isolates in PHC (20000ppm) containing medium, 20 strains were identified based on 16S rDNA sequences belonging to gamma-proteobacteria (10 strains), beta-proteobacteria (6 strains), and alpha-proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes (1 strain each). To confirm the hydrocarbon degradation, 2, 6-dichlorophenol indophenol (2, 6 DCPIP) assay was used, along with spectrophotometric quantification of motor oil degradation and estimation of emulsification index (E_24) of PHC. Four (D05, M012, DO10 and HD2) strains were studied for plant growth promotion (PGP) features by seed germination assay, Vigour Index (VI) and shoot-root assay. Strain DO5 identified as Achromobacter xylosoxidans, showed most promising results amongst the rest of the strains (DO10- Achromobacter sp., HD2- Rhodococcus sp. and M012- Pseudomonas sp.), namely highest degradation of motor oil PHC (94.5%), emulsification index (E_24=52.5%) along with significant enhancement in PGP (VI=520; 54.47% shoot length enhancement and 28.5 % root length enhancement). The study indicates that PHC contaminated soils in urban areas can be a promising source of PHC degrading diverse bacteria that can be applied for dual purpose of soil remediation and plant growth promotion.