Bioremedial potential of bacteria isolated from soil in automobile garages and fuel stations in Mbarara City, Southwestern Uganda

Abstract

The use of bacteria to clean up oil-contaminated soils is widely considered the most desirable bioremediation strategy. The majority of research has focused on contaminated soils in large oil-producing countries. However, accidental spills or poor handling and disposal of petroleum hydrocarbons (PHs) products, which happen at automobile maintenance garages and leakages at fuel stations contaminate soil. There is limited information on PH-degrading bacteria in soil patches around automobile garages and fuel stations for their possible bioremediation potential. We characterized bacteria with the alkane hydroxylase (alkB) gene isolated from soil around automobile repair garages in Mbarara City, Uganda, and assessed their efficiency and effectiveness to degrade PHs. The isolation and identification of cultured bacteria were performed using standard microbiology morphological and biochemical tests. Bacterial efficiency was determined by measuring their growth on used engine oil after 14 days using a turbidometer. The effectiveness of the bacteria was measured after 14 days by dichlorophenol-indophenol redox indicator method. Twelve different genera were identified in 45 bacterial isolates. Enterobacter spp. and Aeromonas spp. were the most effective and efficient bacteria in degrading the used diesel oil, respectively. The alkB-3 gene was identified in 15 bacteria isolates. Two isolates of Yersinia spp and Aeromonas spp showed two genes of 157 bp and 250 bp. These findings are suggestive of the catabolic potential of the isolates to degrade alkanes and require further studies to establish the physicochemical requirements and conditions necessary to ensure the maintenance of an even microbial community composition and diversity needed for successful bioremediation approaches.