Nature and Science 2015;13(2) http://www.sciencepub.net/nature 1 The Synergistic Approach/ Action of Plants and Rhizobacteria in Crude Oil Contaminated Soil Remediation in Nigeria. Ukaegbu-Obi, K.M.* 1 and Mbakwem-Aniebo, C.C. 2 1 Department of Microbiology, College of Natural Sciences, Michael Okpara University of Agriculture, Umudike, P.M.B 7267, Abia State, Nigeria. 2 Department of Microbiology, Faculty of Science, University of Port Harcourt, Choba, Rivers State, Nigeria. *Corresponding author: kelechi.ukaegbuobi@yahoo.com Abstract: The synergistic approach of plants and rhizobacteria in crude oil contaminated soil in three different locations were carried out. The presence of heterotrophic bacteria and hydrocarbon-utilizing bacteria isolated from the polluted and pristine rhizosphere and non-rhizosphere soils of the plants were compared. The polluted rhizosphere of total culturable heterotrophic bacterial count gave a range of 0.98x10 6 cfu/g to 1.37x10 6 cfu/g. The pristine rhizosphere count ranged from 4.11x10 5 cfu/g to 7.55x10 5 cfu/g. The polluted non-rhizosphere gave ranged from 2.39x10 5 cfu/g to 3.28x10 5 cfu/g. The pristine non-rhizosphere had a range of 2.90x10 5 cfu/g to 3.97x10 5 cfu/g. The polluted rhizosphere counts for hydrocarbon-utilizing bacteria ranged from 1.60x10 5 cfu/g to 6.91x10 5 cfu/g. The pristine rhizosphere gave a range of 1.85x10 5 cfu/g to 3.38x10 5 cfu/g. In the polluted non-rhizosphere, the range was from 1.02x10 5 cfu/g to 1.42x10 5 cfu/g. A range of 6.05x10 4 cfu/g to 9.75x10 4 cfu/g was obtained from the pristine non-rhizosphere. There was no significant difference (P>0.05) between the rhizosphere and non-rhizosphere of total heterotrophic and hydrocarbon-utilizing bacterial counts in both polluted and pristine soils. All the plants exhibited positive rhizosphere effects on the rhizobacteria. Hydrocarbon-utilizers were identified as Acinetobacter, Arthrobacter, Alcaligenes, Bacillus, Corynebacterium, Flavobacterium, Micrococcus, Serratia and Pseudomonas spp. All the isolates grew on petroleum hydrocarbon at different growth rates. Based on these results, the organisms isolated can serve as seeds for bioaugmentation during remediation of crude oil polluted soil environment. The plants may be employed in rhizoremediation of oil polluted soil. [Ukaegbu-Obi, K.M. and Mbakwem-Aniebo, C.C. The Synergistic Approach/ Action of Plants and Rhizobacteria in Crude Oil Contaminated Soil Remediation in Nigeria. Nat Sci 2015;13(2):1-5]. (ISSN: 1545- 0740). http://www.sciencepub.net/nature . 1 Keywords: Plants, Synergistic approach, Crude oil, Bacteria, Phytoremediation, Soil, Rhizoremediatio 1. Introduction The usage of petroleum hydrocarbon products has increased soil contamination. This is one of the major environmental problems in Nigeria and globally. Research efforts have been devoted to develop new, low-cost, low-technology, eco-friendly treatments capable of reducing and even eliminating pollution in the atmosphere, the hydrosphere and soil environments (Rao et al., 2010). To investigate the countermeasure to remediate soils contaminated with oils, bioremediation provide such an effective and efficient strategy to speed up the clean-up processes. Bioremediation of contaminated soil is low cost, causes less interference with the soil structure and has a higher public acceptance than other approaches including soil thermal desorption and soil leaching treatment (Tang et al, 2010). Remediation of soils containing organic pollutants can be enhanced by plants by various processes (Cunningham et al., 1996). In-situ phytoremediation strategy exploits natural or genetically engineered plant species to accumulate toxic substances (heavy metals, radioactive compounds, organic pollutants) directly from the soil (Zhou et al., 2011). Partial or complete degradation of organic substances have been demonstrated in some cases (White, 2001). The use of plants to extract, sequester or detoxify pollutants is therefore known as phytoremediation (Gurska, 2009). Plants frequently do not possess complete metabolic degradation pathway for pollutants, and even more toxic by-products may be produced. Most plants have symbiotic relationships with soil microorganisms. For example, root nodule bacteria that have symbiotic relationships with legumes are involved in Nitrogen fixation. The area around plant roots, known as the rhizosphere contains higher populations, greater diversities and activities of microorganisms than soil with no plants (Nicholas et al., 1997). This synergistic approach of using plants and their rhizobacteria in remediation of oil polluted soil is known as rhizoremediation (Kuiper et al., 2004). Application of the synergistic action of plants and their rhizobacteria in crude oil contaminated soil remediation have been demonstrated as an appropriate and more practical alternative to clean-up of