Bo Zhao,Fang Chen,Kexin Zhou,Manfeng Lin,Lihu Shi,Shican Mi,Haixia Pan,Qiang Yao,Xin Zhao
Microplastics and nanoplastics (NPs) are pollutants of global concern. However, the understanding of the combined effects of NPs and other pollutants in the soil-plant system remains limited, particularly for polyethylene (PE), the primary component of agricultural films. This study investigated the effects of PE NPs (0.5%, w/w), fungicide tebuconazole (Te, 10 mg·kg -1 ), and cadmium (Cd, 4.0 mg·kg -1 ) on the soil-wheat system under single and combined exposures. The synergistic toxicity observed between NPs and Te impacted the nutritional conditions and antioxidant mechanisms of the soil-wheat system. The NPs increased the concentration of Cd in roots and the proportion of bioavailable Cd, exacerbating oxidative stress in wheat and inhibiting biomass. The soil-wheat system responded to stress by upregulating or downregulating pathways related to carbohydrate, amino acid, and sugar metabolism under various treatments. Sixteen functional genes associated with carbohydrate metabolism, amino acid metabolism, energy utilization, and gene repair at KEGG level 3 were employed to sustain microenvironmental homeostasis. Correlation analysis between microorganisms and environmental factors showed that various PGPG played roles in maintaining the health of the soil-wheat system. These results help to elucidate the comprehensive effects of NPs with other pollutants on the soil-plant system and provide new perspectives for toxic mechanisms.
The 17β-estradiol (E2)-degrading bacterium Rhodococcus sp.RCBS9 previously showed remarkable resistance to the combined stresses of low temperature and E2. In this study, physiological experiments and transcriptomic analysis were performed to investigate the mechanisms underlying the strain's low-temperature adaptation and briefly analyze how it maintains its ability to degrade E2 at low temperature. The results showed that the strain's signal transduction functions, adaptive changes in cell membrane and cell wall structure, gene repair functions, and synthesis of antioxidants and compatible solutes are key to its ability to adapt to low temperature. In addition, its stress proteins in response to low temperature were not typical cold shock proteins, but rather universal stress proteins (USPs) and heat shock proteins (HSPs), among others. The strain also upregulated biofilm production, transporter proteins for carbon source uptake, and proteins for fatty acid degradation to ensure energy generation. The strain's multiple stress responses work synergistically to resist low-temperature stress, ensuring its adaptability to low-temperature environments and ability to degrade E2. Finally, six genes related to survival at low temperature (identified in the transcriptome analysis) were expressed in E. coli BL21, and they were found to contribute to recombinant E. coli growth at low temperature.
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