Abstract
The crude oil degradability and plasmid profile of autotrophic nitrifying bacteria, Nitrosomonas and Nitrobacter species, isolated from mangrove sediment in the Niger Delta of Nigeria were studied. The effects of temperature, pH and optical density on the utilization of different carbon sources by the bacteria were also investigated. Results showed that nitrifying bacteria could utilize kerosene, diesel oil, jet fuel and engine oil as carbon sources. None utilized hexane and xylene but moderate growth was observed in benzene, phenol and toluene. However, their ability to utilized crude oil varied both in rates of utilization and in growth profiles. Mixed culture of the isolates degrades 52 % of crude oil introduced into the medium followed by Nitrosomonas sp. with 40 % degradation. The least was Nitrobacter sp. with 20 % degradation. The ability of the autotrophs to degrade crude oil was found to be plasmid-mediated through curing experiment and electrophoresis. The size of the plasmid involved was estimated to be 23 kb. The high crude oil utilization of the mixed culture implies that nitrifying bacteria isolated from contaminated ecosystem are excellent crude oil degraders and can be harnessed for bioremediation purposes.
Highlights
The relative capabilities of two bacterial isolates Serratia marcescens OCS-21 and Acinetobacter calcoaceticus COU-27 and yeast isolate; Candida tropicalis PFS-95 in degrading Trans Niger pipeline crude oil has been reported by Ijah (1998)
Diesel and engine oil were purchased from petroleum marketers in Nigeria, while crude oil was obtained from Exxon Mobil Producing Nigeria Unlimited, Eket, Nigeria
This study has shown that Nitrobacter sp. and Nitrosomonas sp. strains isolated from crude oil contaminated mangrove sediment exhibited strong crude oil degradability as indicated by the formation of clearing zones (Fig. 1) and subsequent utilization of crude oil and refined products as sole source of carbon and energy
Summary
Microbiological activity is affected by many environmental factors including energy source, donors and acceptors of electrons, nutrients, pH, and temperature. These parameters influence how quickly microorganisms adapt to the environment (Vieira et al 2007). Hydrocarbon utilizing microorganisms; Micrococcus, Pseudomonas, Bacillus, Aeromonas, Serratia, Proteus, Penicillium, Aspergillus, Candida and Geotrichum have been isolated by enrichment techniques from sediment and water samples collected from oil spill sites in the Niger Delta of Nigeria (Benka-Coker and Ekundayo 1997). The relative capabilities of two bacterial isolates Serratia marcescens OCS-21 and Acinetobacter calcoaceticus COU-27 and yeast isolate; Candida tropicalis PFS-95 in degrading Trans Niger pipeline crude oil has been reported by Ijah (1998). The crude oil-degradability and plasmid profile of nitrifying bacteria from oil-impacted mangrove sediment in the Niger Delta of Nigeria was investigated
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