Toxicity of Soot Against Microorganisms Isolated from Artisanal Crude Oil Refining Sites in the Niger Delta

Background and Objective: Soot is a mass of impure carbon, considered to be an airborne contaminant in areas where artisanal crude oil refining takes place. This study aimed to isolate microorganisms from soot-contaminated plants, water and soil samples within the vicinity of artisanal crude oil operations in Tombia Kingdom, Rivers State, Nigeria. Materials and Methods: Isolates were identified using molecular technique, by comparing their 16S rRNA and ITS genes with previously identified microorganisms in the NCBI data. A biotoxicity assay was conducted to determine the effect of different concentrations (1,10,100, 1000 mg/L) of soot against selected isolates. Microbial growth was monitored for 24, 48, 72 and 96 hrs. Results: Mean concentrations of the heavy metals in soot ranged from 1.29±1.80-25.09±32.51 mg/kg during the wet season and from 8.52±0.20-80.51±0.61 mg/kg during the dry season. The isolates used for the biotoxicity assay closely matched with six bacteria, Enterobacter asburiae (61.6%), Pantoea dispersa (100%), Kocuria rhizophila (98%), Bacillus cereus (98.8%), Bacillus subtilis (100%), Enterobacter bugandensis (100%) and one fungus Exophiala dermatitidis (100%). All isolates were able to grow in the presence of high concentrations of soot, for 96 hrs. Conclusion: Functional genes for hydrocarbon degradation (alkB and PAH) were detected in some of the isolates. The isolates showed tolerance to soot and could be useful in bioremediation of polluted soil.