Investigation of Hydrocarbon-degrading Microbial Communities of Petroleum Hydrocarbon Contaminated Soils in Harghita County, Romania

Microorganisms able to degrade hydrocarbon pollutants (gasoline, and other petroleum derivatives) have been isolated from two contaminated areas (Sândominic and Bălan) by enrichment technique. The hydrocarbon degradative capacity of contaminated sites were determined using “Biometer flasks” (respiratory CO2 production measurement). Total counts and hydrocarbon degrading counts were determined using the MPN method. Isolated strains were tested for their capacity to degrade petroleum derivatives (such as benzene, toluene, xylene, n-dodecane and naphthalene). Those strains which showed great degradation efficiency in case of all investigated hydrocarbons were identified based upon the sequence analysis of their 16S rDNA. Based on the cumulative CO2 production curves it is evident that in the contaminated soil samples there is an increased activity of hydrocarbon degrading microorganisms. During our study we isolated 30 bacterial strains which showed fast growth on at least one of the compounds tested. So far we have identified four strains which could be applicable in bioaugmentation processes. Strains R22 and R31 were identified as Rhodococcus erythropolis; R26 as Micrococcus luteus, R27 as Bacillus cereus and strain R12 as Bacillus subtilis.