Abstract

The soil microbial community plays a huge role in maintaining soil ecosystem balance and soil biological activity, hence a shift in composition or diversity could affect the ecosystem balance. The aim of this study was to examine the change microbial composition and diversity in oil contaminated soil using both traditional and molecular techniques. Bacterial Isolates were morphologically and biochemically characterized, genomic DNA was extracted from isolate and analyzed using 16s rRNA while molecular identification of fungi was performed by sequences analysis from internal transcribed spacer (ITS) region of nuclear ribosomal RNA genes. The 18S rDNA and 28S rDNA fragmens of fungi were analysed and ITS amplified using PCR, microbial isolates were sequenced using sanger sequencer and affiliation of the isolated samples were analyzed by comparing the ITS sequences with those deposited in the GenBank database. The sequence of the isolate demonstrated at least 99% nucleotide identity with the corresponding sequence in GenBank. The Illumina MiSeq high-throughput sequencing technique was used to study the number of reads in the soil. The results showed significant decline in microbial population, composition and diversity in soils under oil pollution when compared with the unpolluted soil. Dominant bacterial isolates belonged to Phylum Firmicutes and Proteobacteria, fungi isolates which belonged to Phylum Ascomcota was dominant in crude oil polluted sites, while Phylum Basidiomycota was dominant in the unpolluted sites. This study also showed that the number of isolates sequenced molecularly was 0.58% of the total metagenomic sequences of all soil samples. Molecular characterization also revealed 5.5% of the bacterial isolates had no significant similarity when blast in NCBI gene bank and those isolates were isolated from mineral salt agar, hence utilized hydrocarbon as energy source, they could be potential novel isolate. Sequences have been submited in the gene bank with accession numbers KT899779-KT899800.

Keywords: 16s RNA; 18s RNA; Crude oil pollution; Phylogyytenic; Microbial population