Characterization of Hydrocarbon-Degrading Microbial Populations in Contaminated and Pristine Alpine Soils

Biodegradation of petroleum hydrocarbons in cold environments, particularly in Alpine soils, is facilitated by indigenous cold-adapted microorganisms capable of degrading these contaminants. The objective of this study was to investigate the prevalence of seven genotypes involved in the degradation of n-alkanes, aromatic hydrocarbons, and polycyclic aromatic hydrocarbons in both contaminated and pristine Alpine soils in Tyrol, Austria. Methodologically, PCR hybridization analyses of total soil community DNA were conducted, supplemented by the use of oligonucleotide primers and DNA probes specific for each genotype across 12 oil-contaminated and 8 pristine soil samples. Results indicated that genotypes containing genes from gram-negative bacteria were significantly more prevalent in contaminated soils (50% to 75%) compared to pristine soils (0 to 12.5%), suggesting enrichment due to contamination. A strong positive correlation was observed between contamination levels and the prevalence of these gram-negative genotypes. Conversely, gram-positive bacteria showed little variation between the two soil types and remained prevalent regardless of contamination status. Notably, no significant association was observed between hydrocarbon-degradative genotypes' prevalence and biological activity metrics, highlighting complex interactions within microbial communities.