Effect of Over a Century of Oil Contamination on Total and Cultivable Bacterial Communities in Arid Desert Soils, Iran
La pollution pétrolière à long terme menace la santé du sol, la biodiversité et les écosystèmes terrestres, particulièrement en environnements arides, où ses effets sur les communautés bactériennes restent peu étudiés. Cette étude réalisée en Iran souligne la nécessité de stratégies de remédiation pour préserver les fonctions écosystémiques.
Springer - 21 Oct 2025
Long-term oil contamination poses a serious threat to soil health, biodiversity, and the stability of terrestrial ecosystems. Despite widespread industrial pollution, the long-term effects of crude oil on soil bacterial communities remain underexplored, especially in arid environments. Understanding how prolonged oil exposure shapes soil microbiota is essential for developing effective remediation strategies and maintaining the soil ecosystem function. In this study, we analyzed changes in total and cultivable soil bacterial communities after over a century of oil contamination. Soil samples were collected from Naft-Shahr, a region in Kermanshah province, Iran, characterized by extensive natural oil seepage and long-term hydrocarbon contamination due to its oil-rich geological formations. Based on the crude oil percentages, the soil samples were categorized into three groups: Low soils (L: 0–7.1% crude oil), Moderate soils (M: 7.2–12.94% crude oil), and High soils (H: > 12.94% crude oil). Cultivable and total soil bacterial communities were analyzed using microbial plating and V3-V5 16S rRNA gene Illumina MiSeq amplicon sequencing. The highest alpha diversity was found in M soils, while the lowest diversity was recorded in H soils. Firmicutes was the dominant bacterial phylum, constituting 94.1%, 13.9%, and 98.8% of the soil bacterial communities in the H, M, and L samples, respectively. Actinobacteria were more abundant in M soils compared to H soils. This indicates that oil concentrations up to around 12% (as in M soils) may favor the development of Actinobacteria, whereas in H soils, with concentrations exceeding 12%, Actinobacteria represented less than 2% of the soil bacterial community. While changes in both alpha-diversity and individual taxa abundances highlighted the impact of high oil pollution on soil bacterial communities, beta-diversity did not show significant differences between L and H soils. This suggests that, despite varying contamination levels, the overall soil bacterial diversity in the contaminated soils remains relatively stable under long-term oil exposure.
