Environmentally Relevant-Level CeO₂ NP with Ferrous Amendment Alters Soil Bacterial Community Compositions and Metabolite Profiles in Rice-Planted Soils

Abstract

The environmental risks and benefits associated with the introduction of CeO 2 nanoparticle (NP) in agricultural soil must be carefully assessed. The ferrous ion is rich in rhizosphere soil of rice due to the reduction states underground. The aim of this study was to investigate the effects of environmentally relevant-level CeO 2 NP (25 mg•kg −1 ) in the absence or presence of ferrous (30 mg•kg −1 ) amendment on soil bacterial communities and soil metabolomics in rice-planted soil over 150 days. Results showed that CeO 2 NP exposure changed soil bacterial community compositions and soil metabolomics, and the above changes were further shifted with the ferrous amendment. Several functionally significant bacterial phyla containing Proteobacteria and Bacteroidetes abundances, which were associated with carbon and nitrogen cycling, were promoted after CeO 2 NP exposure with ferrous amendment. However, CeO 2 NP inhibited plant-growth-promoting rhizobacteria containing genera Bacillus and Arthrobacter irrespective of the presence or absence of ferrous. Among rhizosphere soil enzyme activities, cellulose activity was the most sensitive for CeO 2 NP exposure. NP decreased Firmicutes and increased Chloroflexi, Rokubacteria, and Thaumarchaeota abundances at the phylum level, which contributed to reduce soil cellulose activity. Additionally, CeO 2 NP positively or negatively affected soil pH, Ce accumulation in root, and rice physiological properties (root-POD, stem-POD). As a result, the above factors were related to the changes of Chloroflexi, Gemmatimonadetes, Rokubacteria, Thaumarchaeota, and Nitrospirae at the phylum level. After adding CeO 2 NP with ferrous or not, the main metabolic changes were concentrated on fluctuations in starch and sucrose metabolism, nitrogen metabolism, sulfur metabolism, propanoate metabolism, fatty acid metabolism, and urea cycle. The eight changed metabolites containing glycerol monstearate, boric acid, monopalmitin, palmitic acid, alkane, ethanol, dicarboximide, and stearic acid accounted for the separation of different treatments with CeO 2 NP exposure. Activities of soil enzymes (urease, invertase, and cellulose), pH, and soil organic matter affected dominant metabolites containing fatty acids, inorganic acid, and sugar. Network analysis showed that the influence of soil bacterial community on metabolites varied with metabolites and bacteria species. The presence of CeO 2 NP mainly promoted fatty acids (hexanoic acid, nonanoic acid) and amino acid (oxoproline) and amine (diethanolamine) concentrations, which could be from the increased Proteobacteria abundance after CeO 2 NP exposure. Phylum Proteobacteria had the most genus species containing 13 genera affecting soil metabolite profiles. These results provide valuable information for understanding the impact of environmentally relevant-level CeO 2 NP exposure on soil microbial communities and metabolites with or without ferrous, which is needed to understand the ecological risk posed by long-term CeO 2 NP exposure in rice-planted soil ...

Soil Bacteria and Fungi Respond Differently to Organisms Covering on Leshan Giant Buddha Body

“…For example, no Nitrospirae associated with soil nitrification was found in NR and LR, and its abundance in vascular plant cover was higher than that in bryophyte cover. Interestingly, although Acidobacteria, Chloroflexi and Planctomycetes were more abundant in GS and SS than in other sites, they are commonly used as oligotrophic bacteria [67,68]. This is consistent with previous studies that oligotrophic bacteria are likely to outcompete copiotrophs in environments, for example, the Leshan Giant Buddha, where microorganisms are exposed to constant environmental stress [67,68].…”

“…Interestingly, although Acidobacteria, Chloroflexi and Planctomycetes were more abundant in GS and SS than in other sites, they are commonly used as oligotrophic bacteria [67,68]. This is consistent with previous studies that oligotrophic bacteria are likely to outcompete copiotrophs in environments, for example, the Leshan Giant Buddha, where microorganisms are exposed to constant environmental stress [67,68]. Ascomycetes are the basis of lichen formation, which partly explain the higher abundance of Ascomycota in LR.…”

A microbial consortium‐based product promotes potato yield by recruiting rhizosphere bacteria involved in nitrogen and carbon metabolisms

“…Proteobacteria ranked high in the co‐occurrence network of rhizosphere soil in MCB product treatment plots, and the interaction between Proteobacteria and other bacteria in the rhizosphere bacterial network increased and became more and more complex, indicating that Proteobacteria taxa were important in the microbiota of plots treated with the MCB product. Proteobacteria has been reported to harbour a large group of metabolic enzymes, which have a strong influence on global nitrogen and carbon cycles, as well as soil metabolites due to their great metabolic diversity (Spain et␣al ., 2009; Pan et␣al ., 2020). Prevalent organic substrates, such as amino acids, fatty acids and urea, present in rhizosphere soils were reported to be mainly due to the activity of populations of Proteobacteria (Pan et␣al ., 2020).…”

“…Proteobacteria has been reported to harbour a large group of metabolic enzymes, which have a strong influence on global nitrogen and carbon cycles, as well as soil metabolites due to their great metabolic diversity (Spain et␣al ., 2009; Pan et␣al ., 2020). Prevalent organic substrates, such as amino acids, fatty acids and urea, present in rhizosphere soils were reported to be mainly due to the activity of populations of Proteobacteria (Pan et␣al ., 2020). The high level of relative abundance of Proteobacteria observed was directly associated with increased potato tuber yield.…”

Commonwealth of Soil Health: How Do Earthworms Modify the Soil Microbial Responses to CeO2 Nanoparticles?

“…Soil microbes play crucial roles in the energy flow, nutrient cycling, decomposition, biodiversity, and stability of soil ecosystems . Luo et al and Pan et al reported that CeO 2 NPs had an obvious effect on the soil microbial community structure and inhibited soil dehydrogenase activities at a concentration range of 25–1000 mg/kg. Other NPs, such as Ag NPs, Cu-based NPs, , TiO 2 NPs, and ZnO NPs, , also decreased the microbial activity and changed the bacterial community composition.…”