Search

Membrane vesicles (MVs) contribute to various biological processes in bacteria, including virulence factor delivery, antimicrobial resistance, host immune evasion and cross-species communication. MVs are frequently released from the surface of both Gram-negative and Gram-positive bacteria during growth. In some Gram-positive bacteria, genes affecting MV biogenesis have been identified, but the mechanism of MV formation is unknown. In Enterococcus faecalis, a causative agent of life-threatening bacteraemia and endocarditis, neither mechanisms of MV formation nor their role in virulence has been examined. Since MVs of many bacterial species are implicated in host–pathogen interactions, biofilm formation, horizontal gene transfer, and virulence factor secretion in other species, we sought to identify, describe and functionally characterize MVs from E. faecalis. Here, we show that E. faecalis releases MVs that possess unique lipid and protein profiles, distinct from the intact cell membrane and are enriched in lipoproteins. MVs of E. faecalis are specifically enriched in unsaturated lipids that might provide membrane flexibility to enable MV formation, providing the first insights into the mechanism of MV formation in this Gram-positive organism. Enterococcal MVs possess unique proteome and lipidome and activate NF-kB signaling in macrophages. [ABSTRACT FROM AUTHOR]

Background To control the spread of 2019 novel coronavirus disease (COVID-19), China sealed Wuhan on 23 January 2020 and soon expanded lockdown to 12 other cities in Hubei province. We aimed to describe the epidemiological characteristics in one of the cities and highlight the effect of current implemented lockdown and nonpharmaceutical interventions. Methods We retrieved data of reported cases in Huangshi and Wuhan from publicly available disease databases. Local epidemiological data on suspected or confirmed cases in Huangshi were collected through field investigation. Epidemic curves were constructed with data on reported and observed cases. Results The accumulated confirmed COVID-19 cases and fatality in Huangshi were reported to be 1015 and 3.74%, respectively, compared with 50006 and 5.08% in Wuhan until 27 March 2020. Right after 24 January, the epidemic curve based on observed cases in Huangshi became flattened. And 1 February 2020 was identified as the "turning point" as the epidemic in Huangshi faded soon afterward. COVID-19 epidemic was characterized by mild cases in Huangshi, accounting for 82.66% of total cases. Moreover, 50 asymptomatic infections were identified in adults and children. In addition, we found confirmed cases in 19 familial clusters and 21 healthcare workers, supporting interhuman transmission. Conclusions Our study reported the temporal dynamics and characteristics of the COVID-19 epidemic in Huangshi city, China, across the unprecedented intervention. Such new epidemiological inference might provide further guidance on current lockdown measures in high-risk cities and, subsequently, help improve public health intervention strategies against the pandemic on the country and global levels. [ABSTRACT FROM AUTHOR]

Nitrogen contributes to plant defense responses by the regulation of plant primary metabolism during plant–pathogen interactions. Based on biochemical, physiological, bioinformatic and transcriptome approaches, we investigated how different nitrogen forms (ammonium vs. nitrate) regulate the physiological response of cucumber (Cucumis sativus) to Fusarium oxysporum f. sp. cucumerinum (FOC) infection. The metabolic profile revealed that nitrate-grown plants accumulated more organic acids, while ammonium-grown plants accumulated more amino acids; FOC infection significantly increased levels of both amino acids and organic acids in the roots of ammonium-grown plants. Transcriptome analysis showed that genes related to carbon metabolism were mostly up-regulated in plants grown with nitrate, whereas in ammonium-grown plants the up-regulated genes were mostly those that were related to primary nitrogen metabolism. Root FOC colonization and disease incidence were positively correlated with levels of root amino acids and negatively correlated with levels of root organic acids. In conclusion, organic acid metabolism and expression of related genes increased under nitrate, whereas ammonium increased the level of amino acids and expression of related genes; these altered levels of organic acids and amino acids resulted in different tolerances to FOC infection depending on the nitrogen forms supplied. [ABSTRACT FROM AUTHOR]