Microbial community composition of top and sub soil layers in an aged oil-spill site in Bomu Community, Ogoniland

Abstract

A holistic knowledge of the microbial community structure colonizing different soil depths is essential in designing effective microbial based remediation strategies. Top soil (TS) and sub soil (SS) samples at 0 - 15 cm and 0 - 35 cm depths were collected from an aged crude-oil spilled site in Bomu community, Rivers State characterized with microbiological and physicochemical analytical methods. Samples were enriched in Bushnell Haas broth and screened for the presence of oil-degrading bacteria and fungi. Total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAHs)constituents for TS and SS were 7439.59; 14.58 mg/kg and 8653.03; 1.21 mg/kg, respectively while mean values for hydrocarbon utilizing bacteria and fungi counts for TS and SS were 1.9×10⁵; 0.5×10³cfu/g; and 4.3×10⁵; 0.4×10³cfu/g, respectively. Bacterial and fungal community compositions were identified using phenotypic and microscopic techniques. A total of 24 bacterial species encompassing 11 genera and 10 fungal species from 7 genera were isolated and confirmed as oil degrading microorganisms using biodegradation assay. The bacterial genera for TS included Proteus, Salmonella, Citrobacter, Enterobacter, Klebsiella, Bacillus and Corynebacterium while SS were Escherichia, Flavobacterium, Corynebacterium, Pseudomonas, andBacillus. Gamma Proteobacteria were the dominant class across both soil layers. Fusarium spp. and Rhizopus spp. were the dominant fungal isolates for SS and TS, respectively. The different soil layers were variable in the microbial composition and abundance as well as physical and chemical soil characteristics.

Keywords: Bioremediation, PAHs, TPH, Bomu Community, Ogoniland