Antibiotics susceptibility and hydrocarbon degradative ability of bacteria isolated from diesel-contaminated soil

Abstract

Background: The most commonly used energy resources in the world are the hydrocarbons, which are major sources of environmental pollution. Objectives: This study determined both antibiotics susceptibility pattern and hydrocarbon-degrading capability of bacterial isolates obtained from soil samples contaminated with used diesel. Methods: Serial dilution technique was used to isolate bacterial samples from diesel-contaminated soil samples. Obtained isolates were characterized and identified using appropriate microbiological techniques and were subjected to antimicrobial susceptibility test using disc diffusion assay. The isolates were screened for their ability to utilize hydrocarbon products by streaking pure culture of the isolates on Bushnell Haas agar (BHA) incorporated with 0.5% crude oil. Isolates that showed visible growth within three days were used for degradation studies on hydrocarbon products. Degradation of hydrocarbon products was carried out for 21 days at room temperature while monitoring growth and degradation with appropriate techniques. Results: Forty-one bacterial isolates were obtained from the diesel-contaminated soils, four of which showed visible growth when screened on BHA and these were identified as Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus luteus, and Arthrobacter sp. All the isolates were resistant to Cefriaxome while all the Gram positive isolates were susceptible to Ciprofloxacin. The isolates utilized crude oil at different rates, with Pseudomonas aeruginosa having the highest growth and degradation rate followed by Bacillus sp. while Micrococcus sp. and Arthrobacter sp. showed moderate growth and degradation rate. Conclusion: Pseudomonas aeruginosa obtained from diesel-contaminated soil sample in this study has shown the ability to degrade hydrocarbon products and is a promising candidate for remediating hydrocarbon-contaminated sites.    

Keywords: Bushnell Haas medium, hydrocarbon degradation, gravimetric analysis, spectrophotometry, antibiotics susceptibility