Growth Profile and Catabolic Pathways Involved in Degradation of Aromatic Hydrocarbons by Marine Bacteria Isolated from Niger Delta, Nigeria

Abstract

Aims: To determine the growth profile and catabolic pathways involved in degradation of aromatic hydrocarbons by marine bacteria isolated from Niger Delta, Nigeria. Study Design: Nine treatments designs were set up in triplicate in 500 mL conical flask containing 100 mL of sterile modified mineral basal medium supplemented with three aromatic hydrocarbons (100 mg /L each) and nine marine aromatic hydrocarbon degraders. The treatments were kept in the laboratory and incubated at 24 ºC for 24 days degradation period. The nine treatments and control set ups designated as ANT1, XYL2, PYR3, ANT4, PYR5, ANT6, XYL7, XYL8, PYR9 and CTRL were used to determine the growth profile and metabolic pathways involved in degradation of aromatic hydrocarbons by marine bacteria. Place and Duration of Study: The studied sites were Abonema Wharf Water Front in Akuku-Toru Local Government Area, Nembe Water-side in Port Harcourt Local Government Area and Onne Light Flow Terminal Seaport located in Eleme Local Government Area of Rivers State, Nigeria between September, 2015 and June, 2018. Methodology: A laboratory scale study was carried on six composite samples of the sediment and water samples from the three studied areas using enrichment, screening, selection, molecular characterization, degradation and GC-MS assays. Results: The findings revealed that the sampling sites harbour a lot of efficient aromatic degrading bacterial strains belonging to the genera: Providencia, Alcaligenes, Brevundimonas, Myroides, Serratia, and Bacillus. The bacterial strains were able to significantly (P =.05) degrade simple, low and high molecular weights aromatic hydrocarbons as source of carbon and energy. These strains utilized 100 mg /L of xylene (one ring), anthracene (three rings), and pyrene (four rings) via two main catabolic pathways and catechol is the major constant product that appeared during the degradation period (24 days). Conclusion: Thus, the biodegradation capacities and metabolic pathways obtained from these results suggest that these bacteria especially Serratia marcescens XYL7 could be used efficiently to bioremediate aromatic hydrocarbon contaminated aquatic ecosystems in Nigeria.