Diversity and Metabolic Potential of a PAH-Degrading Bacterial Consortium in Technogenically Contaminated Haplic Chernozem, Southern Russia

Polycyclic aromatic hydrocarbons (PAHs) are chemically recalcitrant carcinogenic and mutagenic compounds with primarily anthropogenic origin. The investigation of the effects of emissions from energy enterprises on soil microbiomes is of a high priority for modern soil science. In this study, metagenomic profiling of technogenic contaminated soils was carried out based on bioinformatic analysis of shotgun metagenome data with PAH-degrading genes identification. The use of prokaryotic consortia has been often used as one of the bio-remediation approaches to degrade PAHs with different molecular weight. Since the process of PAH degradation predominantly includes non-culturable or yet-to-be cultured species, metagenomic approaches are highly recommended for studying the composition and metabolic abilities of microbial communities. In this study, whole metagenome shotgun sequencing of DNA from two soils with varying PAH levels was performed. In the control site, the total content of 12 priority PAHs was 262 mu g kg(-1). The background soil levels in the polluted site for PAHs with 3 or more rings exceeded this, at 800 mu g kg(-1). The abundance of genes and taxa associated with PAH degradation in these two sites were estimated. Despite differences in PAH concentrations up to 1200 mu g kg(-1), individual and operon-organized PAH degradation genes were almost equally abundant and diverse in pristine and highly contaminated areas. The most numerous taxa in both spots were actinobacteria from Terrabacteria group. In addition to well-known PAH degraders such as Gordonia and Rhodococcus, genes corresponding to the PAH degradation were found in Azoarcus, Burkholderia and Variovorax. The data shows non-specificity and multifunctionality of metabolic pathways encoded in the genes of PAH-degrading microorganisms.

Automated summary

This study conducted metagenomic analysis on industrially contaminated soils, revealing that the abundance of PAH degradation genes and taxa did not differ significantly between soils with different pollution levels. The most abundant taxa carrying PAH degradation genes were actinobacteria from the Terrabacteria group. In addition to well-known PAH degraders such as Gordonia and Rhodococcus, other microbes like Azoarcus, Burkholderia, and Variovorax were found to possess genes related to PAH degradation, highlighting the non-specific and multifunctional nature of metabolic pathways encoded in these microorganisms.