Microbial diversity and co-occurrence patterns in deep soils contaminated by polycyclic aromatic hydrocarbons (PAHs)

Area of Science:

• Environmental Microbiology
• Soil Science
• Biogeochemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent soil contaminants.
• Understanding microbial community assembly in contaminated deep soils is crucial for bioremediation.
• Previous research has focused on surface soils, leaving a knowledge gap in deeper contaminated environments.

Purpose of the Study:

• To investigate microbial community structure, diversity, function, and co-occurrence patterns in aged PAH-contaminated deep soil.
• To identify key environmental factors influencing microbial community assembly.
• To determine the role of keystone species in PAH-contaminated deep soil ecosystems.

Main Methods:

• High-throughput sequencing for microbial community analysis.
• Linear Discriminant Analysis of Effect Size (LEfSe) for biomarker identification.
• Tax4Fun for functional gene prediction.
• Statistical correlation analysis and co-occurrence network analysis.

Main Results:

• Dominant bacterial phyla (Proteobacteria, Chloroflexi, Firmicutes, Actinobacteria, Acidobacteria, Nitrospirae) are linked to PAH degradation.
• Edaphic properties (nutrients, pH) significantly correlated with bacterial community and functional composition, more so than PAH concentration.
• Co-occurrence network analysis revealed non-random microbial assembly patterns, with modules involved in nutrient cycling and organic degradation.
• SAR202 clade, Thermoanaerobaculum, Nitrospira, and Xanthomonadales identified as keystone species.

Conclusions:

• Soil nutrients and pH are primary drivers of microbial community assembly in aged PAH-contaminated deep soils.
• Microbial community structure and function are non-randomly assembled, influenced by ecological linkages.
• Keystone species are vital for maintaining the stability and function of these microbial ecosystems.