The joint action of biochar and plant roots on U-stressed soil remediation: Insights from bacteriomics and metabolomics

Degradation of petroleum hydrocarbon contaminants by Rhodococcus erythropolis KB1 synergistic with alfalfa (Medicago sativa L.)

Petroleum hydrocarbons are a stubborn pollutant that is difficult to degrade globally, and plant-microbial degradation is the main way to solve this type of pollutant. In this study, the physiological and ecological responses of alfalfa to petroleum hydrocarbons in different concentrations of petroleum hydrocarbon-contaminated soil with KB1 (Rhodococcus erythropolis) were analyzed and determined by laboratory potting techniques. The growth of alfalfa (CK) and alfalfa with KB1 (JZ) in different concentrations of petroleum hydrocarbons contaminated soil was compared and analyzed. The results of the CK group showed that petroleum hydrocarbons could significantly affect the activity of alfalfa antioxidant enzyme system, inhibit the development of alfalfa roots and the normal growth of plants, especially in the high-concentration group. KB1 strain had the ability to produce IAA, form biofilm, fix nitrogen, produce betaine and ACC deaminase, and the addition of KB1 could improve the growth traits of alfalfa in the soil contaminated with different concentrations of petroleum hydrocarbons, the content of soluble sugars in roots, and the stress resistance and antioxidant enzyme activities of alfalfa. In addition, the degradation kinetics of the strain showed that the degradation rate of petroleum could reach 75.2% after soaking with KB1. Furthermore, KB1 can efficiently degrade petroleum hydrocarbons in advance and significantly alleviate the damage of high concentration of petroleum hydrocarbons to plant roots. The results showed that KB1 strains and alfalfa plants could effectively enhance the degradation of petroleum hydrocarbons, which provided new ideas for improving bioremediation strategies.

Effects of microplastics on carbon release and microbial community in mangrove soil systems

Mangrove ecosystems are major carbon sink biomes and also a sink of microplastics (MPs). The final enrichment of MPs in sediments may have a significant impact on the microbial community and carbon turnover in the soil. However, the effects of MP pollution on the mangrove soil microbial communities and carbon release remain unknown. Here, we conducted a manipulative incubation experiment by adding MPs to soil at different soil depths to examine the effect of enriched MPs on soil microorganisms and its function (i.e., decomposition of soil carbon). The results showed that the addition of MPs had no significant effect on the microbial diversity and CO2 cumulative emission in the topsoil but significantly increased CO2 release from the subsoil. The promoting effect of polylactide (PLA) on the release of CO2 from the subsoil was stronger than that of polyethylene (PE) and aging PE. In the subsoil, the activity of soil extracellular enzymes related to N acquisition increased with the MP addition, indicating an increase in microbial N deficiency. The subsoil was more sensitive to MPs because of the exacerbated nitrogen limitation. MP addition reduced the microbial diversity of the subsoil and altered soil microbial interactions. The increasing abundance of some microbial taxa, especially bacteria related to the sulfur cycle, indicated more active electron transfer and organic carbon mineralization in the subsoil. Our findings suggest that MP contamination has potential effects on microbial communities, nutrient cycling, and carbon release in mangrove soils that vary depending on soil depth.