Urmia Lake: A promising pool of petroleum hydrocarbon biodegrades

In this study, halotolerant microorganisms capable of degrading petroleum hydrocarbons were isolated and analyzed from Urmia Lake. The research focused on identifying microbial consortia resistant to salinity and capable of growing in high concentrations of crude oil. Biodegradation of crude oil at salinity levels ranging from 0% to 27% and concentrations from 1000 to 5000 ppm was evaluated using BOD measurement and GC analysis. The results demonstrated the highest removal efficiency at 3000 ppm crude oil and salinity levels of 0%, 5%, and 10% within 18 days.Metataxonomic analysis of the petroleum hydrocarbon-degrading consortium identified 308,642 sequences, which were clustered into 31,609 OTUs with a 97% similarity threshold. Relative abundance analysis of these sequences revealed the dominance of Salinicoccaceae (57%), Dietziaceae (28.3%), Micrococcaceae (4.2%), and Bacillaceae (3.1%). In metagenomic analysis, whole-genome sequencing data were used for MAG reconstruction and functional gene screening.To isolate pure strains, the crude oil-enriched consortium was cultured on a growth medium, and colonies were isolated after incubation. Among six purified strains, three with higher efficiency were selected for further analysis. 16S rRNA gene sequencing identified these strains as Salinicoccus roseus, Nesterenkonia muleiensis, and Cytobacillus firmus . GC analysis confirmed that Salinicoccus roseus was the most effective hydrocarbon degrader. Although Salinicoccus roseus outperformed the consortium in degrading most petroleum hydrocarbons, the degradation of C26 hydrocarbons required the collective activity of consortium members.