Seasonal co-occurrence patterns of bacteria and eukaryotic phytoplankton and the ecological response in urban aquatic ecosystem

Microorganisms play a key role in aquatic ecosystems.Recent studies show that keystone taxa in microbial community could change the community structure and function.However,most previous studies focus on abundant taxa but neglected low abundant ones.To clarify the seasonal variation of bacterial and microalgal communities and understand their synergistic adaptation to diff erent environmental factors,we studied the bacterial and eukaryotic phytoplankton communities in Fenhe River that runs through Taiyuan City,central China,and their seasonal co-occurrence patterns using 16S and 18S rDNA sequencing.Results indicate that positive interaction of eukaryotic phytoplankton network was more active than negative one except winter,indicating that the cooperation(symbiotic phenomenon in which phytoplankton are interdependent and mutually benefi cial)among them could improve the adaption of microbial community to the local environmental changes and maintain the stability of microbial network.The main genera that identifi ed as keystone taxa in bacterial network were Salinivibrio and Sphingopyxis of Proteobacteria and they could respond to the variation of nitrite and make use of it,while those that identifi ed as keystone taxa in eukaryotic phytoplankton network were Pseudoschroederia and Nannochloris,and they were more susceptible to nitrate and phosphate.Mychonastes and Cryptomonas were closely related to water temperature.However,the loss of the co-occurrence by environmental factor changes aff ected the stability of network structure.This study provided a reference for analyzing relationship between bacteria and eukaryotic phytoplankton and revealing potential importance of keystone taxa in similar ecological domains in carbon,nitrogen,and phosphorus dynamics.

Integrative analysis of the transcriptome and metabolome reveals the mechanism of saline-alkali stress tolerance in Astragalus membranaceus(Fisch)Bge.var.mongholicus(Bge.)Hsiao

Saline-alkali stress is a major abiotic stress affecting the quality and yield of crops.Astragalus membranaceus(Fisch)Bge.var.mongholicus(Bge.)Hsiao(Astragalus mongholicus(A.mongholicus))is a well-known medicine food homology species with various pharmacological effects and health benefits that can grow well in saline-alkali soil.However,the molecular mechanisms underlying the adaptation of A.mongholicus plants to saline-alkali stress have not yet been clarified.Here,A.mongholicus plants were exposed to long-term saline-alkali stress(200 mmol·L^(-1) mixed saline-alkali solution),which limited the growth of A.mongholicus.The roots of A.mongholicus could resist long-term saline-alkali stress by increasing the activity of antioxidant enzymes and the content of osmolytes.Transcriptome analysis(via the llumina platform)and metabolome analysis(via the Nexera UPLC Series QE Liquid Mass Coupling System)revealed that saline-alkali stress altered the activity of various metabolic pathways(e.g.amino acid metabolism,carbohydrate metabolism,lipid metabolism,and biosynthesis of other secondary metabolites).A total of 3690 differentially expressed genes(DEGs)and 997 differentially accumulated metabolites(DAMs)were identified in A..mongholicus roots under saline-alkali stress,and flavonoid-related DEGs and DAMs were significantly upregulated.Pearson correlation analysis revealed significant correlations between DEGs and DAMs related to flavonoid metabolism.MYB transcription factors might also contribute to the regulation of flavonoid biosynthesis.Overall,the results indicate that A.mongholicus plants adapt to saline-alkali stress by upregulating the biosynthesis of flavonoids,which enhances the medicinal value of A.mongholicus.

Mass Transfer during Hematitization and Implications for Uranium Mineralization in the Zoujiashan Deposit,Xiangshan Volcanic Basin

The Zoujiashan uranium deposit in the Xiangshan ore field is the largest volcanic-related uranium deposit in China.Hematite-and fluorite-type ores are the predominant mineralization styles.Hematitization in the Xiangshan ore field is closely associated with uranium mineralization,mainly occurring as hematitized rocks enclosing fluorite-type vein ores developed in pre-ore illitized porphyritic lava.Detailed petrographic and mass balance calculation studies were conducted to evaluate the mechanisms for uranium precipitation and mass transfer during hematitization.Petrographic observations suggest that in the hematitized rocks,orthoclase is more altered than plagioclase,and quartz dissolution is common,whereas in the illitized rocks,pyrite commonly occurs within the altered biotite grains,and chlorite grains are locally found.Mass balance calculations indicate that Na2O and U were gained,K2O,Ca O and Si O2were lost,whereas Fe2O3-t remained more or less constant during hematitization.These observations suggest that the hydrothermal fluids were Na-and U-rich and Ca-K-poor,and the Fe2+used for hematitization was locally derived,most likely from biotite,pyrite and chlorite in the host rocks.The Fe2+is inferred to have played the role of reductant to precipitate uranium,and calculation indicates that oxidation of Fe2+provided by host rocks is sufficient to form ores of economic significance.Consequently,the hematite-type ore is interpreted to be generated by the reaction between oxidized ore fluids and reduced components in host rocks.The development of calcite and pyrite in the fluorite ores suggests that perhaps mixing between the U-rich fluid and another fluid carrying reduced sulfur and carbon may have also contributed to uranium mineralization,in addition to temperature and pressure drop associated with the veining.