Microbial Degradation of Petroleum Hydrocarbons: Realities, Challenges and Prospects

One of the emerging environmental challenges today is hydrocarbon pollution arising from activities of petrochemical industries, natural sources of crude oil pollution and other anthropogenic activities. These petroleum products contain harmful, carcinogenic and mutagenic compounds which could have severe consequences on biotic and abiotic components of the ecosystem. Physicochemical and biological methods are employed for the remediation of hydrocarbon contaminated systems; however, the negative impacts of the physicochemical approach are presently directing greater attention to the exploitation of the biological alternatives. This article reviews basic concepts of petroleum hydrocarbons, hydrocarbon degrading microorganisms, factors that influence the biodegradation of contaminants and innovative technologies for the effective removal of these pollutants. This article also discusses the applications of relative advances in molecular biological techniques, such as the isolation of plasmid DNA of microbial communities and the use of genetically engineered microorganisms to increase the rates of biodegradation of hydrocarbon pollutants in the environment.

Bacterial Community Profile and Phylogenetic Diversity of Water and Surface Sediments in Iko River Estuary, Akwa Ibom State- Nigeria

A large amount of crude oil is spilled annually into the terrestrial and aquatic environments in Nigeria. This tends to upset the natural equilibrium of the marine environment as a microbial habitat. Thus, there is a need to evaluate the effect of exposure to crude oil on bacterial load and diversity using Iko River and Odoro Ikot pond as the study and pristine sites respectively. The bacterial isolates were molecularly identified using the 16S rRNA sequencing protocol. The total heterotrophic bacterial count (THBC) in the surface water (SW), sub-surface water (SSW) and sediment segments of Iko River ranged from 2.23±0.87 to 9.67 ± 0.43 x 106 CFU/ML while the THBC in the SW, SSW and sediment segments of the pristine site (Odoro Ikot pond) ranged from 1.87±0.53 to 4.8± 0.04x106 CFU/ML. The sediment had a significantly higher (P<0.05) THBC than the water segments (SW and SSW) in both Iko River and Odoro Ikot pond. The hydrocarbon utilizing bacteria (HUB) count in Odoro Ikot pond ranged from 0.40 ± 0.01 to 1.10 ± 0.03 x 106 CFU/ML while the HUB count in Iko River ranged from 0.53 ± 0.02 to 0.93 ± 0.04 x 106 CFU/ML, making Iko River have a higher number of total heterotrophic bacteria and hydrocarbon utilizing bacteria than Odoro Ikot pond. The Proteobacteria isolates had the highest bacterial diversity (77%) while members of the Firmicutes phylum had a 23% bacterial diversity. However, higher bacterial count and diversity were obtained from the sediment segment than from the water segments in both Iko River and Odoro Ikot pond implying that the sediment is more favourable for bacterial growth. Although the bacterial profile was affected by exposure to crude oil, there were variations in the phylogenetic diversities obtained from the different water segments attributable to crude oil concentration.