Cysteine and thiosulfate promoted cadmium immobilization in strain G303 by the formation of extracellular CdS.

Bacteria have evolved a variety of strategies to defend themselves against cadmium toxicity, however, the specific mechanisms involved in the enhancement of bacterial cadmium resistance by sulfur sources are unclear. In this study, a novel cadmium (Cd)-tolerant bacterium, Stenotrophomonas geniculata G303, was isolated from activated sludge. The growth of strain G303 under diverse Cd concentrations was investigated, and the minimum inhibitory concentration of Cd was found to be 1 mM. Strain G303 effectively remove 94.7 % of Cd after 96 h of culture. Extracellular CdS was detected using multiple methods, with the CdS formed being aggregated in the biofilm. The addition of cysteine and thiosulfate to the medium significantly enhanced the Cd resistance and removal capacity of strain G303. Integrated genomic and proteomic analyses revealed that heavy metal transporters cooperate to resist Cd stress. Cysteine and thiosulfate improved Cd tolerance in strain G303 by upregulating nitrogen and energy metabolism. Proteins associated with nitrate reduction likely played a pivotal role in cysteine and thiosulfate metabolism. Notably, cysteine synthase and the SUF system played crucial roles in CdS formation. This study systematically explored the impact of cysteine and thiosulfate on the Cd resistance of strain G303, deepening our understanding of the microbial response mechanism to heavy metals.

Harmonizing international quality standards for Andrographis paniculata: A comparative analysis of content determination methods across pharmacopeias.

The quality standards for Andrographis paniculata, a widely used medicinal herb, exhibited significant variations across different pharmacopeias. In this study, we compared the HPLC content determination methods and total lactone content of A. paniculata samples from different regions, as specified in the Chinese (CP), United States (USP), European (EP), Thai (TP), and Indian pharmacopeias (IP), as well as the Hong Kong Chinese Materia Medica Standards (HK). We aimed to assess the differences and similarities among these pharmacopeias and harmonized international quality standards for A. paniculata. The analysis revealed variations in sample preparation, liquid chromatographic conditions, fingerprint profiles, and total lactone content among the different pharmacopeias. Specifically, the CP and HK methods exhibited superior sample preparation and chromatographic separation. Further comparing the content of 20 A. paniculata samples with the CP, USP, EP and HK methods showed consistent determinations for the same components, indicating similar detection capabilities. The discrepancies in total lactone content primarily stemmed from differences in the number and types of detected compounds. Moreover, the acceptance criteria exhibited a stringency in the order CP > HK > EP > USP. In conclusion, this comparison analysis of content determination in CP, USP, HK, EP, TP and IP provided a scientific foundation for the international standardization and trade regulations of A. paniculata. It also served as a valuable reference for the development of international quality standards for other medicinal herbs, facilitating the harmonization of global pharmaceutical standards.

Soil organic carbon decomposition responding to warming under nitrogen addition across Chinese vegetable soils.

Chemical fertilization in excess and warming disrupt the soil microbes and alter resource stoichiometry, particularly in intensive vegetable soils, while the effects of these variables on the temperature sensitivity of soil organic carbon (SOC) decomposition (Q10) and SOC stability remain elusive. Thus, we collected six long-term vegetable soils along a climatic gradient to examine the microbial mechanisms and resource stoichiometry effects on fluctuations in Q10 and SOC stability induced by warming and fertilization from vegetable soils. Our results showed that the SOC decomposition was dominated by microbes and regulated by stoichiometry. Compared to cold sites, higher Q10 of SOC decomposition was observed in warm sites, accompanied by lower enzyme activities, microbial CUE, and C:N ratio. In this context, warming reduced SOC stability as evidenced by up to 31.8% greater Q10 (1.45) at warm sites than at cold sites (1.10) owing to less richness of microbial communities and lower microbial CUE. The relatively lower pH and labile organic C value restricted the development of microbial richness, and decreased C- and N-related enzyme activities and a lower C:N ratio resulted in microbial CUE reduction. Additionally, N fertilization altered the C:N imbalance and enhanced SOC stability in vegetable soils, exhibiting an increase of Q10 values, particularly of great importance in warm sites. Collectively, our findings emphasize the importance of the microbial mechanism and resource stoichiometry in predicting variations in Q10 and fluctuations in SOC stability, and provide theoretical advice on improving management policies in the context of warming and fertilization from vegetable soils.

N2O and NO production and functional microbes responding to biochar aging process in an intensified vegetable soil.

Vegetable soils with high nitrogen input are hotspots of nitrous oxide (N2O) and nitric oxide (NO), and biochar amended to soil has been documented to effectively decrease N2O and NO emissions. However, the aging effects of biochar on soil N2O and NO production and the relevant mechanisms are not thoroughly understood. A15N tracing microcosm study was conducted to clarify the responses of N2O and NO production pathways to the biochar aging process in vegetable soil. The results showed that autotrophic nitrification was the predominant source of N2O production. Biochar aging increased the O-containing functional groups while lowering the aromaticity and pore size. Fresh biochar enhanced the AOB-amoA gene abundance and obviously stimulated N2O production by 15.5% via autotrophic nitrification and denitrification. In contrast, field-aged biochar markedly weakened autotrophic nitrification and denitrification and thus decreased N2O production by 17.0%, as evidenced by the change in AOB-amoA and nosZI gene abundances. However, the amendment with artificially lab-aged biochar had no effect on N2O production. With the extension of aging time, biochar application reduced the soil NO production dominated by nitrification. Changes in the N2O and NO fluxes were closely associated with soil NH4+-N and NO2--N contents, indicating that autotrophic nitrification played a critical role in NO production. Overall, our study demonstrated that field-aged biochar suppressed N2O production via autotrophic nitrification and denitrification by regulating associated functional genes, but not for lab-aged biochar or fresh biochar. These findings improved our insights regarding the implications of biochar aging on N2O and NO mitigation in vegetable soils.