ABSTRACT

Isolation and molecular characterization of hydrocarbon degrading bacteria from Okulu river in Eleme Local Government area, Rivers state were studied. Wastewater samples were randomly collected at four different points in the river using a 2 litre plastic hydrobios water sampler and aseptically transferred into sterile 2-litre plastic containers. Standard methods were adopted for the determination of microbiological and physico-chemical characteristics. The identification of bacteria isolates were carried out using both morphological and biochemical characteristics. Also isolates were molecularly characterized. The abilities of the bacterial isolates to degrade total petroleum hydrocarbon were determined using Gas chromatographic method. The total heterotrophic bacteria count in Okulu River ranged from 1.8×10⁶ - 2.2×10⁷ cfu/ ml.  Hydrocarbon utilizing bacteria count recorded ranged from 1.0×10³ – 4.2×10⁴ cfu/ ml. The predominant bacterial genera identified were Bacillus, Micrococcus, Escherichia, Staphylococcus, Pseudomonas, Enterobacter, Klebsiella, Streptococcus, Pectobacterium, Bevibacillus, Serratia and Providencia species.  The pH values in Okulu water samples ranged from 6.11 - 6.65, with mean value of 6.35±01.8. The temperature values ranged from 28.3 - 32.7 ^oC, with mean value of 31.04±1.72 ^oC. The turbidity ranged from 17.7 - 112 NTU, with mean value of 54.69±31.55 NTU. Values for total dissolved solids ranged from 22.1 - 58.9 mg/l, with mean value of 44.08 mg/l±12.63. Total suspended solids ranged from 6.01 – 8.77 mg/l, with mean value of 6.98mg/l±1.18. Biological oxygen demand ranged from 20.25 - 46.50 mg/l, with mean value of 32.85±10.62 mg/l. The chemical oxygen demand showed ranges of 29.37 - 66.52 mg/l, with mean value of 50.84±14.89 mg/l. Dissolved oxygen ranged from 2.28 - 4.37 mg/l, with mean value of 3.19 ±0.70 mg/l. Salinity ranged from 15.0 - 22.5 mg/l, with mean value of 18.23 ±2.65 mg/l. Conductivity values had range of 3.53 - 3.88 µS/cm, with mean value of 3.71±0.09 µS/cm. Nitrate values ranged from 2.18 - 4.21 mg/l, with mean value of 3.02±0.66 mg/l. Values of phosphate ranged from 2.58 - 4.11 mg/l, with mean value of 3.47 ±0.47mg/l. Total organic carbon had range of 1.12 - 2.70 %, with mean value of 1.92±0.55 %.  Total hydrocarbon content values ranged from 13.27 - 17.70 mg/l, with mean value of 15.52 ±1.87 mg/l. For the heavy metals, lead values in the samples ranged from 2.0107 - 2.0857 mg/l, with mean value of 2.03553±0.02 mg/l. Values of cadmium ranged from 0.1639 - 0.3157 mg/l, with mean value of 0.233508±1.72 mg/l. Arsenic values in Okulu water samples ranged from 0.0154 - 0.0381 mg/l, with mean value of 0.0345±1.72 mg/l. The obtained 16S rRNA sequence of the bacteria produced close relatedness to their relatives from the NCBI data base. Based on their 16S rRNA sequence, the bacteria were identified as Lysinibacillus fusiformis, Alcaligenes faecalis, Enterobacter cloacae, Lysinibacillus sphaericus and Lysinibacillus macroides. The bioremediation potential of the bacteria isolates gave positive results singularly and in combination in terms of degradation of hydrocarbon content of the water sample. These bacteria isolated from Okulu River can be used for the remediation of polluted environment. In view of the results obtained, the test bacterial species can be applied in the remediation of polluted environment especially hydrocarbon-polluted environment