Tea biochar-immobilized Ralstonia Bcul-1 increases nitrate nitrogen content and reduces the bioavailability of cadmium and chromium in a fertilized vegetable soil

A new strategy for removing insecticide etoxazole from soil using a combination of a novel Paracoccus versutus Y4 and a fungal mycelium carrier

Etoxazole is a widely used insecticide that poses a serious threat to both ecosystems and human health. In present study, a novel strain Paracoccus versutus Y4 was isolated and identified. More than 98 % of the etoxazole (10 mg/L) was degraded as the sole carbon source within 8 d by strain Y4 in liquid culture. HPLCMS/MS analysis revealed three possible intermediates, and a novel metabolic pathway of etoxazole including oxidation, dehydrogenation, and hydrolysis reactions was proposed. The Toxicity Estimation Software Tool suggests that the biodegradation intermediates were less harmful than etoxazole. Whole-genome sequencing revealed that the genome size of P. versutus Y4 was 5320,902 bp containing 5187 coding sequences. Among them, the gene coding monooxygenase, dehydrogenase and hydrolase may be responsible for etoxazole biodegradation. The results of molecular docking analysis suggested that the monooxygenase, dehydrogenase, and hydrolase from strain Y4 may facilitate catalytic degradation through efficient substrate binding. Compared with diatomite carrier, fungal mycelium carrier can promote the growth of strain Y4. In the soil degradation experiments, the fungal mycelium carrier promoted etoxazole degradation by strain Y4 in both fresh and sterilized soil. Treatment with Y4 +fungal mycelium significantly reduced the half-life of etoxazole in fresh soil from 24.2 to 6.3 d. Our study is the first to isolate etoxazole-degrading bacteria and provides a new strategy for the bioremediation of pesticide pollution by combining degrading microbes and fungal mycelium carriers.

Deep application of controlled-release urea increases the yield and saponin content of Panax notoginseng by regulating soil nitrate distribution

Introduction

The deep application of controlled-release urea (CRU) offers potential advantages for crops with extended growth periods. However, its effects on P. notoginseng yield and quality, a medicinal plant with a prolonged nutrient acquisition duration, remain unclear.

Methods

In this study, we conducted a two-year field plot experiment to investigate the effect of CRU on P. notoginseng with three placement depths (0, 6, and 12 cm denoted as R0, R6, and R12, respectively) at an application dosage of 250 kg N ha-1 with biochar addition (R6B) and 20% N reduction (R6R) based on the R6, with conventional fertilization (250 kg N ha-1, common urea) serving as the control (CK).

Results

Our results indicated that yields increased by 27.1-37.6% with R0, R6, R12, and R6B, while remaining stable with R6R compared to CK. Simultaneously, the total saponin content in the roots of R6, R6B, and R6R was improved by 14.3-38.1%, compared to CK. The distribution depth of soil NO3 ⁻-N and plant roots increased with the depth of CRU application, with a high overlap in time and space, indicating P. notoginseng N uptake peaked when CRU was applied at a depth of 6 cm (R6). Structural equation modeling indicated that soil NO3 ⁻-N supply in specific microareas directly affected the N uptake and increased total saponin content by increasing root length and surface area, thus boosting yield.

Conclusion

This study identifies that the deep application of CRU at a depth of 6 cm has the potential to enhance both yield and quality of P. notoginseng and highlights that the spatial-temporal matching of soil NO₃⁻-N and plant roots was the key to applying CRU to ensure high yield and quality.

Combined biochar and wheat-derived endophytic bacteria reduces cadmium uptake in wheat grains in a metal-polluted soil

In this study, two wheat-derived cadmium (Cd)-immobilizing endophytic Pseudomonas paralactis M14 and Priestia megaterium R27 were evaluated for their effects on wheat tissue Cd uptake under hydroponic conditions. Then, the impacts of the biochar (BC), M14+R27 (MR), and BC+MR treatments on wheat Cd uptake and the mechanisms involved were investigated at the jointing, heading, and mature stages of wheat plants under field-plot conditions. A hydroponic experiment showed that the MR treatment significantly decreased the above-ground tissue Cd content compared with the M14 or R27 treatment. The BC+MR treatment reduced the grain Cd content by 51.5%-67.7% and Cd translocation factor at the mature stage of wheat plants and increased the organic matter-bound Cd content by 31%-75% in the rhizosphere soils compared with the BC or MR treatment. Compared with the BC or MR treatment, the relative abundances of the biomarkers associated with Gemmatimonas, Altererythrobacter, Gammaproteobacteria, Xanthomonadaceae, Phenylobacterium, and Nocardioides in the BC+MR-treated rhizosphere microbiome decreased and negatively correlated with the organic matter-bound Cd contents. In the BC+MR-treated root interior microbiome, the relative abundance of the biomarker belonging to Exiguobacterium increased and negatively correlated with the Cd translocation factor, while the relative abundance of the biomarker belonging to Pseudonocardiaceae decreased and positively correlated with the Cd translocation factor. Our findings suggested that the BC+MR treatment reduced Cd availability and Cd transfer through affecting the abundances of these specific biomarkers in the rhizosphere soil and root interior microbiomes, leading to decreased wheat grain Cd uptake in the contaminated soil.

Zinc and cadmium change the metabolic activities and vegetable cellulose degradation of Bacillus cellulasensis in vegetable soils

Bacillus cellulasensis Zn-B isolated from vegetable soil was highly adaptable to Zinc (Zn) and Cadmium (Cd). Cd, but not Zn, adversely affected the total protein spectrum and functional groups of Bacillus cellulasensis Zn-B. Up to 31 metabolic pathways and 216 metabolites of Bacillus cellulasensis Zn-B were significantly changed by Zn and Cd (Zn&Cd). Some metabolic pathways and metabolites related to functional groups of sulfhydryl (-SH) and amine (-NH-) metabolism were enhanced by Zn&Cd addition. The cellulase activity of Bacillus cellulasensis Zn-B was up to 8.58 U mL^-1, increased to 10.77 U mL^-1 in Bacillus cellulasensis Zn-B + 300 mg L^-1 Zn, and maintained at 6.13 U mL^-1 in Bacillus cellulasensis Zn-B + 50 mg L^-1 Cd. The vegetables' cellulose content was decreased by 25.05-52.37% and 40.28-70.70% under the action of Bacillus cellulasensis Zn-B and Bacillus cellulasensis Zn-B + 300 mg L^-1 Zn. Those results demonstrated that Zn could significantly enhance cellulase activity and biodegradability of Bacillus cellulasensis Zn-B to vegetable cellulose. Bacillus cellulasensis Zn-B can survive in vegetable soil accumulated with Zn&Cd. The tolerance concentration and adsorption capacity of Bacillus cellulasensis Zn-B to Zn were up to 300 mg L^-1 and 56.85%, indicating that Bacillus cellulasensis Zn-B acting as a thermostability biological agent had an essential advantage in accelerating the degradation of discarded vegetables by Zn and were beneficial to maintain organic matter content of vegetable soil.