Effects of bacterial-feeding nematodes on soil microbial activity and the microbial community in oil-contaminated soil.

Abstract Rapid economic development has caused an increase in serious pollution problems due to the ever-increasing use of oil and its products, thus making oil pollution control an urgent task. Studies have shown that large amounts of bacterial-feeding nematodes are present in oil-contaminated soil; their function is as yet unclear. In this experiment, different densities of Caenorhabditis elegans (C. elegans) were inoculated into artificially simulated oil-contaminated soil to examine their effects on microbial activity and the microbial community in oil-contaminated soil. Six treatments were investigated: sterilized oil-contaminated soil as control 1 (FSP), nematode-free soil as control 2 (S), oil-contaminated soil (SP), oil-contaminated soil + 5, 10 or 20 individual C. elegans per gram of dry soil (i.e., SPN5, SPN10, SPN20). Results showed that oil pollution significantly increased the soil basal respiration. However, C. elegans weakened the soil basal respiration to different degrees and soil microbial respiration entropy essentially changed in line with the soil basal respiration. Oil pollution and C. elegans boosted catalase activity in contaminated soil by approximately 64.2–145.1%. Soil urease activity of SPN5, SPN10 and SPN20 was 88.5%, 126.7% and 109.0% stronger, respectively, than that of SP. The inoculation of C. elegans changed the microbial phospholipid fatty acid content in the oil-contaminated soil, including soil bacteria, fungi, actinomycetes, Gram-positive bacteria (G+) and Gram-negative bacteria (G−). Therefore, this research demonstrates that C. elegans can stimulate microbial reproduction in oil-contaminated soil, enhance related soil enzyme activities and regulate soil microbial community structure and diversity, thereby improving the contaminated soil environment and promoting oil degradation. Graphical abstract Effects of different densities of C. elegans on oil degradation. Bacterial-feeding nematodes are rich in oil-contaminated soils, but their functions remain unclear. In this study, different densities of Caenorhabditis elegans were inoculated into simulated oil-contaminated soil to examine their effects on the microbial activity and the microbial community. Results demonstrated that C. elegans addition stimulated the oil degradation and improved the repair efficiency of oil-contaminated soil. However, the magnitudes of effects did not increase as the inoculating density of C. elegans increased. Our findings suggest that C. elegans with an appropriate density would affect soil microbial growth and reproduction, thus enhancing the efficiency of oil degradation. Image 1 Highlights • C. elegans are added into soil to test the effects on microbes and oil degradation. • C. elegans and oil pollution can change the microbial activity and community. • C. elegans can promote the oil degradation in contaminated soil. [ABSTRACT FROM AUTHOR]