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The degradation capacity of Xanthomonas campestris on crude oil, petrol, diesel and kerosene and the effect of monoammonium phosphate (MAP) addition on biodegradation efficiency were investigated in this study. X. campestris was identified using 16S rRNA sequencing while the concentration of the test compounds was determined via gas chromatography. Higher cell densities and viable bacterial counts were obtained in the presence of MAP. No significant differences (p≤0.05) were seen in counts between the two MAP application concentrations of 150 mg L-1 and 250 mg L-1. Statistically significant differences (p≤0.05) were, however, observed between the set-ups with MAP added and those without. At the end of the study, it was ascertained that addition of MAP improved the efficiency of biodegradation by up to 5.86% – 14.44% at 150 mg L-1 MAP application level and 11.11% – 15.83% at 250 mg L-1 MAP concentration. The greatest increase was seen with petrol (14.2% – 15.8%) which was also the most readily degraded of the test compounds. Biodegradation half-lives were also improved by up to 8.8 days on average in the presence of MAP. Fractions C26 – C30 proved to be the most recalcitrant based on mean removal percentages. The findings suggest that X. campestris was able to effectively breakdown the test hydrocarbon complexes and the addition of MAP enhanced its biodegradation efficiency. The bacterium may, therefore, be applied to bioremediation of environmental media polluted by crude oil or its derivative hydrocarbon fuels.