Bacteriological and heavy metal assessment of a tropical crude oil- polluted soil, water and sediment

Crude oil-polluted environment serves as a reservoir of microbial species, especially bacteria. Determining these bacterial genera is of great benefit to environmental assessment and recovery. This study evaluated the bacteria and selected heavy metals present in crude oil-polluted sites in K-dere community, Ogoniland. The study was carried out at the Department of Microbiology, University of Port Harcourt, Rivers State, Nigeria. Crude oil-polluted soil, water, and sediment samples were collected from K-dere community, Ogoniland. The pH and heavy metals composition of each sample was determined using pH meter and spectrophotometer, respectively, while isolation and biochemical characterization were done to evaluate the heterotrophic and hydrocarbon utilizing bacteria present in each sample. Results revealed that iron (Fe) had the highest concentration in the soil (898.77±0.022 mg/kg) and sediment (1556.7±0.163 mg/kg) samples, while lead (Pb) had the lowest overall concentration. The concentration of total petroleum hydrocarbon (TPH) (10410.5 mg/kg) in soil sample exceeded the DPR standard limit of 5000 mg/kg for soil. The results of total culturable heterotrophic bacterial counts (TCHBC) and total culturable hydrocarbon utilizing bacterial counts (TCHUBC) showed that soil and sediment samples had the highest TCHBC and TCHUBC values of 2.66 ± 0.03 x 108 CFU/mL and 4.7 ± 0.14 x 107 CFU/mL respectively. Morphological and biochemical characterization of the isolates revealed the presence of Pseudomonas spp, Bacillus spp, Acidiphilium spp, Mycobacterium spp and Leptospirillum spp in the samples with Pseudomonas spp having the highest percentage occurrence. This study has revealed the presence of useful bacterial species in the sampled sites which can be harnessed for an in situ cleaning of crude oil- contaminated site, especially in the tropical region.