Microbial community composition in petroleum-contaminated and uncontaminated soil from Francisco de Orellana, in the northern Ecuadorian Amazon

The microbial compositions of two soils from the northern Ecuadorian Amazon (Francisco de Orellana province), one contaminated with petroleum and the other uncontaminated, were compared. Classical culture and molecular techniques were used to analyze microbial diversity. The cultivable Bacteria from contaminated soil belonged to betaproteobacteria (16.6%), gammaproteobacteria (66.6%), and Firmicutes (16,6%), whereas in uncontaminated soil, cultivable Bacteria were identified as gammaproteobacteria (80%) and Firmicutes (20%). Analysis of the 16S rRNA showed that in the contaminated soil proteobacterial populations (alpha-, beta- and deltaproteobacteria) were more abundant than acidobacterial populations. The Shannon index (H′) was used to estimate diversity in the contaminated and uncontaminated soil. Diversity was higher in the uncontaminated (H′ =2.16) than in the contaminated (H′ = 1.72) soil sample. Further studies are needed to determine whether the differences between contaminated and non-contaminated soil samples were due to spontaneous bioremediation microbial activity.