Identification of Catabolic Genes Involved in the Degradation of Used Engine Lubricant- Contaminated Soil by Lysinibacillus odysseyi and Bacillus sp. (in: firmicutes)

This study aimed to identify selected catabolic genes in two indigenous hydrocarbon-degrading bacteria involved in the biodegradation of used engine lubricant-contaminated soil. Used engine lubricant-contaminated and uncontaminated soil samples were collected, and their physicochemical characteristics were evaluated. The results indicated that water holding capacity, potassium, nitrogen, and phosphate were higher in used lubricant-uncontaminated soil than in used lubricant-contaminated soil but vice versa for pH, total carbon, cation exchange, organic carbon, nickel, and lead levels. Culturable heterotrophic and hydrocarbon-utilizing bacterial counts were carried out on both Nutrient agar and Mineral Salt Medium (MSM) amended with used engine lubricant. The counts for heterotrophic bacteria (3.8×108±0.21 cfu/gm) were higher than that of hydrocarbon-utilizing bacteria (2.2×108±0.15 cfu/gm). All isolated bacteria (16) underwent screening for hydrocarbon degradation potential. Lysinibacillus odysseyi and Bacillus sp (in: firmicutes) emerged as the best oil degraders. Further screening of the chromosomal and plasmid DNA of the two bacteria was done to determine the presence and location of some selected catabolic genes (NidA, AlkB, NahH, NahAC, and Alma). The presence of Alkane monooxygenase (AlkB) and Naphthalene dioxygenase (NahAC) genes was confirmed in both isolates, while Pyrene dioxygenase (NidA) was confirmed in Bacillus sp. (in: firmicutes) only. The location of AlkB was confirmed to be both plasmid and chromosome, while NidA and NahAC genes were confirmed to be the plasmid. In conclusion, the soil contaminated with used engine lubricant contained indigenous bacteria, Lysinibacillus odysseyi, and Bacillus sp. (in: firmicutes), the two bacteria with the highest degradation potential, contained catabolic genes, monooxygenase (AlkB), NidA, and dioxygenase (NahAC). Therefore, they are effectively used as engine lubricant degraders, and the possibility of horizontal gene transfer can be used in important industrial applications and is recommended for the bioremediation of petroleum compounds.