Polyphasic microbial community analysis of petroleum hydrocarbon-contaminated soils from two northern Canadian communities

The cold-adapted bacterial communities in petroleum hydrocarbon-contaminate d and non-impacted soils from two northern Canadian environments, Kuujjuaq, Que,, and Alert, Nunavut, were analyzed using a polyphasic approach. Denat uring gradient gel electrophoresis (DGGE) separation of 16S rDNA PCR fragme nts from soil total community DNA revealed a high level of bacterial divers ity, as estimated by the total number of bands visualized. Dendrogram analy sis clustered the sample sites on the basis of geographical location. Compa rison of the overall microbial molecular diversity suggested that in the Ku ujjuaq sites, contamination negatively impacted diversity whereas in the Al ert samples, diversity was maintained or increased as compared to uncontami nated controls. Extraction and sequencing analysis of selected 16S rDNA ban ds demonstrated a range of similarity of 86-100% to reference organisms, wi th 63.6% of the bands representing high G+C Gram-positive organisms in the order Actinomycetales and 36.4% in the class Proteobacteria. Community leve l physiological profiles generated using Bioiog GN plates were analyzed by cluster analysis. Based on substrate oxidation rates, the samples clustered into groups similar to those of the DGGE dendrograms, i.e. separation base d upon geographic origin. The coinciding results reached using culture-inde pendent and -dependent analyses reinforces the conclusion that geographical origin of the samples, rather than petroleum contamination level, was more important in determining species diversity within these cold-adapted bacte rial communities. Published by Elsevier Science B.V. on behalf of the Feder ation of European Microbiological Societies.