*Corresponding author: ausbones@gmail.com, ausbones@iuokada.edu.ng https://doi.org/10.36547/ae.2020.2.2.12-16 Abstract The capability of indigenous bacteria and microalgae in crude oil effluents to grow in and utilize crude oil as their sole source of carbon and energy provides an environmentally friendly and economical process for dealing with crude oil pollution and its inherent hazards. In view of the toxicity of crude oil spillages to indwellers of the affected ecosystems and the entire affected environment, the isolation of pure bacterial and microalgae cultures from crude effluents is a step in the right direction, particularly for bio- augmentation or bioremediation purposes. The total heterotrophic bacteria count and hydrocarbon utilizing bacteria count, as well as the microalgae count, were determined with the pour plate technique. The physicochemical properties of the effluent samples were also analyzed. Identification of the hydrocarbon utilizing bacteria was performed with phenotypic techniques. The result shows a mean total heterotrophic bacterium count of 5.91 log CFU/ml and a mean microalga count of 4.77 log cells/ml. When crude oil and polycyclic aromatic hydrocarbon (PAH) were used as sole carbon sources, total hydrocarbon utilizing bacteria counts were respectively estimated at 3.89 and 2.89 log CFU/ml. Phenotypic identification of hydrocarbon utilizing bacteria in the crude oil effluents revealed the presence of two main bacterial genera: Streptococcus and Pseudomonas. Data obtained from this study confirmed the biodegradative abilities of indigenous bacterial species, thus, ultimately resulting in the amelioration of the toxicity associated with the crude oil effluents. Archives of Ecotoxicology, Vol. 2, No. 2, pp. 12-16, 2020 Isolation and Characterization of Crude Oil Degrading Bacteria in Association with Microalgae in Saver Pit from Egbaoma Flow Station, Niger Delta, Nigeria Akpoka, O. A. a* , Erifeta, G. O. b , Imade, O. S. a , Okafor-Elenwo, E. J. a , Enaigbe, A. A. a , Abolarin, D. S. a a Department of Biological Science, College of Natural and Applied Sciences, Igbinedion University, Okada, Nigeria. b Department of Biochemistry, College of Natural and Applied Sciences, Igbinedion University, Okada, Nigeria. 1. Introduction Petroleum hydrocarbons have undoubtedly emerged as significant environmental contaminants (Eriyamremu et al., 2007; Liu et al., 2010). Environmental pollution especially oil spills are major threats predominantly in the Niger Delta region of Nigeria, due to intensive exploration and other petroleum related legal and illegal activities resulting in several environmental hazards ranging from soil infertility, erosion of soil microbial diversity and total damage to both flora and fauna in the environment (Nweke and Okpokwasili, 2004; Head et al., 2006; Emtiazi et al., 2009; Mittal and Singh, 2009). Despite the immense economic benefit of crude oil, oil spills in soils have been traceable to various hazards in the environment and could cause several diseases like Kidney disease, probable destruction of the bone marrow and a risk factor in cancer due to the presence of harmful carcinogenic and mutagenic substances (Lichtfouse et al., 1997; Lloyd et al., 2001; Mishra et al., 2001; Sing and Lin, 2008), and even death in lower animals (Phyllis et al., 1989; Eriyamremu et al., 2007). The high demand for petroleum products contributes to the increase in crude oil extraction, processing and large amounts of oily waste through various means. Crude oil is a complex mixture of chemicals varying widely in their composition of hydrocarbon and hydrocarbon-like (polycyclic aromatic hydrocarbons; PAH) chemicals and may persist in the environment for prolonged periods, posing a major threat to ecosystems. Biodegradation by intrinsic microbial populations is one of the reliable tools through which a great deal of xenobiotic contaminants, comprising crude oil spill and effluents are gradually degraded and subsequently eradicated from the environment (Cappello et al., 2007). The catabolic abilities of microorganisms such as fungi, bacteria and algae to degrade petroleum hydrocarbons had been previously reported (Wang et al., 2011); these microorganisms possess specific enzyme systems that enable them to degrade and utilize hydrocarbons as their carbon and energy sources. The most important means of aerobic PAH biodegradation is the primary oxidation of the aromatic benzene ring through which molecular oxygen is incorporated by the dioxygenase enzymes to form cis-dihydrodiols. The intermediates of dihydrodiol dehydrogenation are metabolized to carbon dioxide and water through the catechols by the actions of catechol dioxygenases and other enzymes (Chikere et al., 2011). However, one of the major limitations of (PAHs) Archives of Ecotoxicology Journal homepage: https://office.scicell.org/index.php/AE Keywords: Crude oil Oil Degrading Bacteria Microalgae Crude oil effluents Polycyclic aromatic hydrocarbon Article info Received 15 October 2019 Revised 12 May 2020 Accepted 27 May 2020 Published online 3 June 2020 Regular article