Yujie Wang,Peng Li,Yunhe Tian,Ziqin Xiong,Zhongyi Zheng,Zhenxie Yi,Hejun Ao,Qiming Wang,Juan Li
Cadmium (Cd) contamination in rice ( Oryza sativa ) is particularly problematic due to its high risk to human health. Investigating the hidden roles of seed endophytes of rice in influencing Cd accumulation is essential to comprehensively understand the effects of biotic and abiotic factors to food security. Here, the content of Cd in soils and rice (Huanghuazhan) seeds from 19 sites along the Yangtze River exhibited considerable differences. From a biotic perspective, we observed the dominant endophytic bacteria, Stenotrophomonas (7.25 %), contribute to Cd control of rice (below 0.2 mg kg −1 ). Partial Least Squares (PLS) analysis further suggested that Enterobacteriaceae (15.48 %), altitude and pH were found to be the strong variables that might reduce the Cd uptake of rice. In contrast, Cytophagaceae (0.58 %), latitude and mean annual air pressure had the opposite effect. In pot experiments, after respectively inoculating the isolated endophytic bacteria Stenotrophomonas T4 and Enterobacter R1, N1 (f_Enterobacteriaceae), the Cd contents in shoot decreased by 47.6 %, 21.9 % and 33.0 % compared to controls. The distribution of Cd resistant genes (e.g., czcABC, nccAB, cznA ) of Stenotrophomonas, Enterobacteriaceaea and Cytophagaceae further suggested their distinct manners in influencing the Cd uptake of rice. Overall, this study provides new insights into the food security threatened by globally widespread Cd pollution.
Jie Hou,Chao Hu,Yanlong Wang,Jianying Zhang,Jason C. White,Kun Yang,Daohui Lin
The biological effect of soilborne nanoparticles (NPs) is a manifestation of soil-NMs-bio interactions. Soil factors are known to restructure NPs surfaces and thus influence the nanotoxicity. However, the mechanisms by which environmental factors affecting nano-bio interactions to aggravate or alleviate nanotoxicities are poorly understood. Herein, we compared the toxicity of TiO 2 NPs (nTiO 2 ) in five soils using the model nematode ( Caenorhabditis elegans ), and investigated the variation of nano-bio interactions under different conditions. A correlation analysis showed that pH and dissolved organic matter (DOM) were dominant regulators of nTiO 2 toxicity. At the nano-bio interface, low pH (5.0) led to nTiO 2 adhesion to micron-sized furrows and aggravated dermal wrinkling, while humid acid (HA) alleviated these impacts. Mechanically, low pH increased nTiO 2 adhesion through enhanced electrostatic attraction and subsequent stimulation of mucin and collagen synthesis, resulting in a positive feed cycle of pH-dependent contact nanotoxicity. HA not only prevented nTiO 2 adhesion onto the epidermis due to its negative charge, but also relieved the overstimulation of stress response pathways, thereby alleviating nanotoxicity. These findings broaden our knowledge of how NPs induce contact toxicity in soil invertebrates through specific biointerfacial interactions, and highlight the important role of DOM in alleviating the combined hazards of NPs and soil acidification.
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