The mechanism of SARS-CoV-2 egress predominantly governs the quantity and quality of progeny viruses, thereby significantly contributing to viral pathogenicity. However, the key factors influencing viral egress remain largely unclear. In this study, using transcription- and replication-competent SARS-CoV-2 virus-like-particle (SARS-CoV-2 trVLP), electron microscopy, drug inhibition assays, and cellular pH-sensitive fluorescent probes, we demonstrate that increased lysosomal exocytosis efficiency and lysosome deacidification play a pivotal role in facilitating SARS-CoV-2 egress. Specifically, SARS-CoV-2 may use multiple egress pathways, with lysosomal exocytosis as the primary mechanism and the biosynthetic secretory pathway as a less efficient route. Viral infection enhances lysosomal exocytosis via the ORF3a protein, thus facilitating viral release. SARS-CoV-2 infection also induces lysosome deacidification; moreover, treatment with bafilomycin A1, which induces lysosome deacidification, further enhances viral egress. Furthermore, we systematically investigate how viral proteins affect lysosomal pH and enzymatic activities. Our findings reveal that ORF3a and E proteins induce lysosome deacidification and diminish lysosomal enzyme activities, probably protecting progeny viruses from premature cleavage and degradation. This study provides mechanistic insight into how SARS-CoV-2 promotes lysosomal exocytosis and triggers lysosome deacidification for viral release.

Gut microbiota composition is suggested to associate with coronavirus disease 2019 (COVID-19) severity, but the impact of gut microbiota on health outcomes is largely unclear. We recruited 81 individuals from Wuhan, China, including 13 asymptomatic infection cases (Group A), 24 COVID-19 convalescents with adverse outcomes (Group C), 31 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) re-positive cases (Group D), and 13 non-COVID-19 healthy controls (Group H). The microbial features of Groups A and D were similar and exhibited higher gut microbial diversity and more abundant short-chain fatty acid (SCFA)-producing species than Group C. Group C was enriched with opportunistic pathogens and virulence factors related to adhesion and toxin production. The abundance of SCFA-producing species was negatively correlated, while Escherichia coli was positively correlated with adverse outcomes. All three groups (A, C, and D) were enriched with the mucus-degrading species Akkermansia muciniphila, but decreased with Bacteroides-encoded carbohydrate-active enzymes. The pathways of vitamin B6 metabolic and folate biosynthesis were decreased, while selenocompound metabolism was increased in the three groups. Specifically, the secondary bile acid (BA) metabolic pathway was enriched in Group A. Antibiotic resistance genes were common among the three groups. Conclusively, the gut microbiota was related to the health outcomes of COVID-19. Dietary supplementations (SCFAs, BA, selenium, folate, vitamin B6) may be beneficial to COVID-19 patients.

The objective of the study was to elucidate optical characteristics of the chromophore structures of fluorescent proteins. Raman spectra of commonly used GFP-like fluorescent proteins (FPs) with diverse emission wavelengths (green, yellow, cyan and red), including the enhanced homogenous FPs EGFP, EYFP, and ECFP (from jellyfish) as well as mNeptune (from sea anemone) were measured. High-quality Raman spectra were obtained and many marker bands for the chromophore of the FPs were identified via assignment of Raman spectra bands. We report the presence of a positive linear correlation between the Raman band shift of C₅=C₆ and the excitation energy of FPs, demonstrated by plotting absorption maxima (cm⁻¹) against the position of the Raman band C₅=C₆ in EGFP, ECFP, EYFP, the anionic chromophore and the neutral chromophore. This study revealed new Raman features in the chromophores of the observed FPs, and may contribute to a deeper understanding of the optical properties of FPs.

Protein nanocages are ideal templates for the bio-inspired fabrication of nanomaterials due to several advantageous properties. During the mineralization of nanoparticles (NPs) inside protein nanocages, most studies have employed a common strategy: seed formation inside protein nanocages followed by seeded NP growth. However, the seed formation step is restricted to gentle reaction conditions to avoid damage to the protein nanocages, which may greatly limit the spectrum of seed materials used for NP growth. We put forward a simple route to circumvent such a limitation: encapsulation of a preformed NP as the seed via self-assembly, followed by the growth of an outer metal layer. Using such a method, we succeeded in mineralizing size-tunable Au NPs and Au@Ag core–shell NPs (< 10 nm in diameter) with narrow size distributions inside the virus-based NPs of simian virus 40. The present route enables the utilization of NPs synthesized under any conditions as the starting seeds for nanomaterial growth inside protein nanocages. Therefore, it potentially leads to novel bioinorganic chimeric nanomaterials with tailorable components and structures.