Biostimulation Shaped Microbial Communities in Oil-contaminated Desert Soils

Oil contamination poses serious environmental challenges, particularly in hyper-arid desert ecosystems; yet, microbial responses to oil pollution and biostimulation in desert soils remain insufficiently explored. This study explored the microbial community dynamics and hydrocarbon degradation potential to oil contamination and biostimulation in desert soils collected from sites in southern Israel polluted in 1975 and 2014. Laboratory-based biostimulation experiments were conducted over 1.5 years, involving the addition of water (20% or 50% gravimetric saturation), nutrients, and biosurfactants. Results revealed that biostimulation treatments reduced microbial diversity but enriched populations capable of hydrocarbon degradation. Proteobacteria and Actinobacteria were the dominant phyla, comprising 68% to 78% of the total microbial community across both contamination timelines. The relative abundance of Chloroflexi was higher in biostimulated contaminated soils, showing an increase of 41% to 227% compared to untreated contaminated soils. Differential abundance analysis identified distinct taxa of hydrocarbon degraders associated with untreated contaminated soils (e.g., Pseudomonas, Alkanindiges, Bacillus, and Mycobacterium) and biostimulated contaminated soils (e.g., Pseudomonas, Flavobacterium, Pseudoxanthomonas, unclassified Microbacteriaceae, Solimonadaceae, and Gammaproteobacteria). Further, soil hydrophobicity and total petroleum hydrocarbon suggested a positive relationship with the abundance of the nahAc gene, a key marker of hydrocarbon degradation. These findings exhibit that targeted biostimulation with water, nutrients, and biosurfactants accelerates oil biodegradation while selectively reshaping microbial communities toward hydrocarbon degrading taxa in hyper-arid desert soils. This study points to the potential development of effective management and remediation strategies for oil-contaminated desert environments.