Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens.

In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO22+, referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe3+ ion. The results show that the production of mineralized solids {hydrogen-uranium mica [H2(UO2)2(PO4)2·8H2O]} via S. putrefaciens binding with UO22+ is inhibited by DFO, which can both chelate preferentially UO22+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe3+ ion introduced, the strong specificity of DFO binding with Fe3+ causes re-emergence of biomineralization of UO22+ {bassetite [Fe(UO2)2(PO4)2·8(H2O)]} by S. putrefaciens, owing to competitive complexation between Fe3+ and UO22+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe3+ and UO22+ ions via these functional groups. The stability of the Fe3+-DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO22+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.

Uranium speciation and distribution on the surface of Shewanella putrefaciens in the presence of inorganic phosphate and zero-valent iron under anaerobic conditions.

Shewanella putrefaciens (S. putrefaciens) is one of the main microorganisms in soil bioreactors, which mainly immobilizes uranium through reduction and mineralization processes. However, the effects of elements such as phosphorus and ZVI, which may be present in the actual environment, on the mineralization and reduction processes are still not clearly understood and the environment is mostly in the absence of oxygen. In this study, we ensure that all experiments are performed in an anaerobic glove box, and we elucidate through a combination of macroscopic experimental findings and microscopic characterization that the presence of inorganic phosphates enhances the mineralization of uranyl ions on the surface of S. putrefaciens, while zero-valent iron (ZVI) facilitates the immobilization of uranium by promoting the reduction of uranium by S. putrefaciens. Interestingly, when inorganic phosphates and ZVI co-exist, both the mineralization and reduction of uranium on the bacterial surface are simultaneously enhanced. However, these two substances exhibit a certain degree of antagonism in terms of uranium immobilization by S. putrefaciens. Furthermore, it is found that the influence of pH on the mineralization and reduction of uranyl ions is far more significant than that of inorganic phosphates and ZVI. This study contributes to a better understanding of the environmental fate of uranium in real-world settings and provides valuable theoretical support for the bioremediation and risk assessment of uranium contamination.

Mechanism of lead adsorption by a Bacillus cereus strain with indole-3-acetic acid secretion and inorganic phosphorus dissolution functions.

BACKGROUND: Heavy metal pollution has become a major source of environmental pollution because of increasing industrialization. Microbial remediation is a promising approach to remediate lead-contaminated environments owing to its cost-effective, environment-friendly, ecologically sustainable, and highly efficient properties. In this study, the growth-promoting functions and lead-adsorption ability of Bacillus cereus SEM-15 were examined, and the functional mechanism of the strain was preliminarily identified using scanning electron microscopy, energy spectrum, infrared spectrum, and genome analyses, providing theoretical support for utilization of B. cereus SEM-15 in heavy metals remediation. RESULTS: B. cereus SEM-15 showed strong ability to dissolve inorganic phosphorus and secrete indole-3-acetic acid. The lead adsorption efficiency of the strain at lead ion concentration of 150 mg/L was more than 93%. Single factor analysis revealed the optimal conditions for heavy metal adsorption by B. cereus SEM-15 (adsorption time, initial lead ion concentration, pH, and inoculum amount were 10 min, 50-150 mg/L, 6-7, and 5 g/L, respectively) in nutrient-free environment, with the lead adsorption rate reaching 96.58%. Scanning electron microscopy of B. cereus SEM-15 cells before and after lead adsorption showed adherence of a large number of granular precipitates to the cell surface after lead adsorption. X-Ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results indicated the characteristic peaks of Pb-O, Pb-O-R (R = functional group), and Pb-S bonds after lead adsorption, and a shift in the characteristic peaks of bonds and groups related to C, N, and O. Genome annotation results showed the presence of genes related to heavy metals tolerance and plant growth promotion in B. cereus SEM-15, providing a molecular basis for the strain's heavy metals tolerance and plant growth promotion functions. CONCLUSIONS: This study analyzed the lead adsorption characteristics of B. cereus SEM-15 and the associated influencing factors, and discussed the adsorption mechanism and related functional genes, providing a basis for clarifying the underlying molecular mechanism and offering a reference for further research on plant-microorganisms combined remediation of heavy metals polluted environments.

Phylogenetic Analysis of the Complete rRNA Gene Sequence of Nosema sp. SE Isolated from the Beet Armyworm Spodoptera exigua.

The microsporidium Nosema sp. SE is a pathogen that infects the beet armyworm Spodoptera exigua. The complete sequence of its 4,302-base pair (bp) ribosomal ribonucleic acid (rRNA) gene region was obtained by polymerase chain reaction amplification and sequencing. The rRNA organization of Nosema sp. SE was 5'-large subunit (LSU) rRNA-internal transcribed spacer-small subunit (SSU) rRNA-intergenic spacer-5S-3', which corresponded to the pattern of Nosema bombycis. Phylogenetic analysis based on LSU rRNA and SSU rRNA both indicated that the parasite had a close relationship with other true Nosema species, confirming that Nosema sp. SE belongs to true Nosema group of the genus Nosema.

Quality Formation Mechanism of Stiff Silkworm, Bombyx batryticatus Using UPLC-Q-TOF-MS-Based Metabolomics.

Bombyx batryticatus is a well-known animal in traditional Chinese medicine. The aim of the research was to reveal the quality formation mechanism of B. batryticatus and to screen out the characteristic component used for the quality control. The anticonvulsant effects of B. batryticatus with a stiff time of one, five, and nine days (D1, D5 and D9, respectively) and healthy silkworm of the same developmental stage (SW) were determined by animal experiment. The dynamic changes in chemical composition were analyzed using UPLC-Q-TOF-MS-based metabolomics. D5 and D9 B. batryticatus exhibited significant anticonvulsant effects (p < 0.05 and p < 0.01, respectively). Accordingly, principal component analysis (PCA) and partial least squares discrimination analysis (PLS-DA) indicated that the chemical composition of D5 and D9 B. batryticatus changed significantly. The different metabolites mainly consisted of primary metabolites such as lipids and amino acids and secondary metabolites such as flavonoids, beauvericin, and glycolipids. Interestingly, the relative abundance of quercetin-7-O-ß-d-4-O-methylglucoside, the characteristic component of B. batryticatus, increased with stiff time and was promised to be used as an index component of quality control. The results expand our understanding of the quality formation mechanism of B. batryticatus. In addition, it highlights the potential of UPLC-Q-TOF-MS-based metabolomics for the quality control purpose of TCMs.

Icariin induces apoptosis by suppressing autophagy in tamoxifen-resistant breast cancer cell line MCF-7/TAM.

BACKGROUND: Icariin is a major component isolated from Epimedium brevicornum Maxim and has been reported to exhibit anti-tumor activity. However, whether icariin could reverse the acquired drug resistance in breast cancer remains largely unclear. Therefore, this study was designed to explore the antitumor effects of icariin and its underlying mechanisms in a tamoxifen-resistant breast cancer cell line MCF-7/TAM. METHODS: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Lactate dehydrogenase (LDH) assay were performed to determine the effects of icariin on cell viability and cell death. Cell cycle progression and apoptosis were detected by flow cytometry analysis. Transmission electron microscopy (TEM) assay was utilized to observe cell autophagy. The downstream protein levels were measured using western blotting. RESULTS: Here, we observed that icariin treatment not only inhibited the growth of MCF-7 but also has a potential function to overcome tamoxifen resistance in MCF-7/TAM. Moreover, icariin significantly induced cell cycle G0/G1 phase arrest and apoptosis, as well as suppressed autophagy. At molecular levels, icariin treatment remarkably down-regulated the expression levels of CDK2, CDK4, Cyclin D1, Bcl-2, LC3-1, LC3-II, AGT5, Beclin-1, but upregulated the expression levels of caspase-3, PARP and p62. Most importantly, we found inhibition of autophagy via 3-MA treatment could significantly enhance the effects of icariin on cell viability and apoptosis. Enhanced autophagy via autophagy related 5 (ATG5) overexpression could partially reverse the effects of icariin on cell viability and apoptosis. CONCLUSION: These results revealed that icariin might potentially be useful as an adjuvant agent in cancer chemotherapy to enhance the effect of tamoxifen through suppression of autophagy in vitro and provide insight into the therapeutic potential of icariin for the treatment of chemo-resistant breast cancer.

Simplified recovery of enzymes and nutrients in sweet potato wastewater and preparing health black tea and theaflavins with scrap tea.

The industry discards generous organic wastewater in sweet potato starch factory and scrap tea in tea production. A simplified procedure to recover all biochemicals from the wastewater of sweet potato starch factory and use them to make health black tea and theaflavins from scrap green tea was developed. The sweet potato wastewater was sequentially treated by isoelectric precipitation, ultrafiltration and nanofiltration to recover polyphenol oxidase (PPO), ß-amylase, and small molecular fractions, respectively. The PPO fraction can effectively transform green tea extracts into black tea with high content of theaflavins through the optimized fed-batch feeding fermentation. The PPO transformed black tea with sporamins can be used to make health black tea, or make theaflavins by fractionation with ethyl acetate. This work provides a resource- and environment-friendly approach for economically utilizing the sweet potato wastewater and the scrap tea, and making biochemical, nutrient and health products.