Isolation and Characterization of Hydrocarbonoclastic Bacteria from Diesel Contaminated Environment: A Case Study from Mashasha Garage, Katsina State, Nigeria

Hydrocarbonoclastic bacteria play crucial roles in natural attenuation of petroleum hydrocarbon contamination in the environment. Paenibacillus species are characterized by their ability to form endospores, produce various enzymes, and survive in harsh environmental conditions, making them particularly suitable for hydrocarbon-contaminated environments. This study aimed to isolate and characterize hydrocarbonoclastic bacteria from diesel-contaminated soil collected from Mashasha Garage, Katsina State, Nigeria. Soil samples were collected aseptically and cultured on Bushnell-Haas agar supplemented with 2.5% diesel as the sole carbon source. Pure bacterial isolates were identified using the VITEK-2 Compact automated identification system. Fresh bacterial cultures were suspended in sterile saline to achieve appropriate turbidity standards. Bacterial growth kinetics were evaluated using mineral salt broth (MSB) supplemented with different diesel concentrations The isolated bacterium demonstrated strong growth on hydrocarbon-supplemented media, forming large, off-white, rough colonies. Microscopic analysis revealed rod-shaped, Gram-positive, motile, endospore-forming cells characteristic of the Paenibacillus genus. Biochemical and molecular identification confirmed the isolate as Paenibacillus polymyxa. The bacterium exhibited efficient growth in diesel-supplemented media across various concentrations (100-1000 ppm), with optimal growth observed at 500 ppm concentration. Growth kinetics analysis revealed the highest specific growth rate (0.26192 hr⁻¹) at 500 ppm diesel concentration during the exponential phase. The finding supports the concept that hydrocarbon-utilizing bacteria are widely distributed in environments with petroleum exposure and suggests that local microbial communities may possess inherent bioremediation potential that could be harnessed for environmental restoration efforts. The study demonstsrate the successful isolation of a hydrocarbonoclastic bacterium from diesel-contaminated environments, contributing to the understanding of indigenous microbial communities capable of hydrocarbon utilisation.