Biodegradative activities of some gram- negative bacilli isolated from kerosene treated soil grown with cowpea (Vigna unguiculata)

Abstract

The biodegradative activities of three Gram negative bacilli (Aeromonas hydrophila, Vibro parahaemolyticus and Actinobacillus sp) isolated from soil contaminated with kerosene and planted with cowpea was investigated. The isolates were identified using MicrobactTM ID 24E system for the identification of Enterobacteriaceae and common miscellaneous Gram negative bacilli (MGNB). 2kg of soil collected from University of Ilorin was placed inside transparent, drilled buckets. Physicochemical properties of the soil were recorded. The soil was contaminated with kerosene at different concentrations of 0ml, 7ml, 14ml, 21ml, 56ml, 112ml, 168ml and 224ml. The setup was laid out in a randomized complete block design with three replicates. Cowpea seeds of the variety Samaru-40 were cultivated and observed for eight weeks. The results indicated that kerosene contamination of soils significantly affected the growth parameters: germination percentage, time of germination, rate of germination, plant height, number of leaves, leaf area and root nodules. A negative interaction existed between the level of the contaminant and the growth characteristics measured. Their biodegradative activities were studied and confirmed by the change in the Total Petroleum Hydrocarbon (TPH) using gravimetric method. The biodegradative abilities of the isolates were compared by measuring the optical densities, total viable count, pH and emulsification activity. The results showed that the organisms did better as a consortium rather than singly. Aeromonas hydrophila had the highest biodegradative activity followed by Vibro parahaemolyticus and then Actinobacillus sp. The study recommends the use of Aeromonas hydrophila and consortium for more effective biodegradation. Keywords: Bacterial Biodegradation, Soil, Cowpea, Kerosene, Total Petroleum Hydrocarbon