Insect guts offer unique habitats for microbial colonization, with gut bacteria potentially offering numerous benefits to their hosts. Although Enterococcus has emerged as one of the predominant gut commensal bacteria in insects, its establishment in various niches within the gut has not been characterized well. In this study, Enterococcus mundtii was inoculated into the silkworm (Bombyx mori L.) to investigate its biological functions. Genome-based analysis revealed that its successful colonization is related to adherence genes (ebpA, ebpC, efaA, srtC, and scm). This bacterium did not alter the activities of related metabolic enzymes or the intestinal barrier function. However, significant changes in the gene expressions levels of Att2, CecA, and Lys suggest potential adaptive mechanisms of host immunity to symbiotic E. mundtii. Moreover, 16S metagenomics analysis revealed a significant increase in the relative abundance of E. mundtii in the intestines of silkworms following inoculation. The intestinal microbiome displayed marked heterogeneity, an elevated gut microbiome health index, a reduced microbial dysbiosis index, and low potential pathogenicity in the treatment group. Additionally, E. mundtii enhanced the breakdown of carbohydrates in host intestines. Overall, E. mundtii serves as a beneficial microbe for insects, promoting intestinal homeostasis by providing competitive advantage. This characteristic helps E. mundtii dominate complex microbial environments and remain prevalent across Lepidoptera, likely fostering long-term symbiosis between the both parties. The present study contributes to clarifying the niche of E. mundtii in the intestine of lepidopteran insects and further reveals its potential roles in their insect hosts.

The utilization of nitenpyram for aphid and whitefly control may induce environmental contamination and negative repercussions on non-target organisms. Formerly, we found that nitenpyram would pollute the peripheral and sub-peripheral areas of the adjacent mulberry orchard. Under acute toxicity conditions, nitenpyram induced oxidative damage in silkworms, affected biological metabolism, synthesis, immunity, and signal transduction. Considering the impact of nitenpyram mist drift on mulberry leaves, we investigated the effects of low concentrations of nitenpyram on silkworms. The results showed that silkworms exposed to 0.17 mg/L, 0.35 mg/L and 0.70 mg/L of nitenpyram (1/40 LC50, 1/20 LC50 and 1/10 LC50) showed obvious poisoning symptoms. The cocoon weight and cocoon shell weight decreased gradually with increases in the concentration, and these decreases prolonged the growth and development time of silkworms and induced the detoxification enzymes carboxylesterase (CarE) and glutathione-S-transferase (GST) to cope with the stress damage caused by nitenpyram. Exposure to low concentrations of nitenpyram downregulates genes involved in the drug metabolism-other enzymes and peroxisome pathway in silkworms. Additionally, through injection of miRNA mimics and inhibitors, we discovered that detoxifying enzyme pathway genes are influenced by bmo-miR-3382-3P, bmo-miR-3213-5P and bmo-miR-133, regulating the immune response of silkworms. This study provides an overall view of the toxicity and detoxification metabolism of nitenpyram in silkworm, and provides a reference for environmental assessment.

Microsporidia are opportunistic fungal-like pathogens that cause microsporidiosis, which results in significant economic losses and threatens public health. Infection of domesticated silkworms by the microsporidium Nosema bombycis causes pébrine disease, for which this species of microsporidia has received much attention. Research has been conducted extensively on this microsporidium over the past few decades to better understand its infection, transmission, host-parasite interaction, and detection. Several tools exist to study this species including the complete genome sequence of N. bombycis. In addition to the understanding of N. bombycis being important for the silkworm industry, this species has become a model organism for studying microsporidia. Research on biology of N. bombycis will contribute to the development of knowledge regarding microsporidia and potential antimicrosporidia drugs. Furthermore, this will provide insight into the molecular evolution and functioning of other fungal pathogens.

BmNPV is a pathogen that infects silkworms exclusively. Although the interaction between BmNPV and the silkworm has been widely noticed and studied, its specific mechanism has still not been elucidated. In this study, we investigated whether BmNPV infection induces the onset of host cell autophagy to enhance viral replication. We observed a significant increase in double- or single-membrane vesicles and an accumulation of enhanced green fluorescent protein eGFP-ATG8 spots in virus-infected cells 72 h after BmNPV infection, accompanied by a conversion of ATG8 to ATG8-PE. In addition, we observed changes in the mitochondrial morphology of BmN cells after BmNPV infection by transmission electron microscopy. By detecting the mitochondrial membrane potential, we found that BmNPV infection resulted in the decrease of mitochondrial membrane potential, and that eGFP-ATG8 was able to co-localise with mitochondria after virus infection of the cells. Moreover, the use of drugs to regulate the occurrence of autophagy affects the replication of cellular BmNPV. Our data demonstrates that BmNPV infection induces host cell autophagy and leads to cellular mitochondrial damage, which in turn may lead to mitochondrial autophagy, and that BmNPV-induced host autophagy promotes its replication in cells. These findings will provide clues for further understanding of host-virus interactions.

The extensive utilization of bismuth and its derivatives in many industries, such as chemical, semiconductor, pharmaceutical, and cosmetics, leads to their accumulation in wastewater, posing a risk to both human health and the environment. Carbon nanorods (CNR) are fluorescent nanoparticles with an ability to detect various analytes as sensing probes. This study focuses on the production, structure, and chemical composition characterization of silkworm-derived CNR (swCNR) and their ability to detect bismuth ions (Bi3+) and inhibit radicals. The optimum wavelength for exciting the fluorescence of swCNR was 370 nm, and the resulting emission peak was observed at 436 nm. The prepared swCNR showed static fluorescence quenching mechanism-based sensing of Bi3+ ions with a limit of detection of 175 nM and two linear ranges from 0.5 to 5 μM (R2 = 0.9997) and 10-50 μM (R2 = 0.9995). The swCNR demonstrated high selectivity in detecting Bi3+ ions in the spiked river water samples, thus establishing the swCNR\'s role as a nano fluorescence probe designed for the selective detection of Bi3+ ions among other metal ions. Favorable results for the antiradical ability of swCNR were obtained against hydroxyl, 2,2 diphenyl-1 picrylhydrazyl, and 2,2\'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals with scavenging percentages of 15, 32, and 90, respectively. The possible applications of swCNR in the environmental and antioxidant sectors are proposed in this study.

n-3 Long-chain polyunsaturated fatty acids (n-3 LC-PUFAs), including eicosapentaenoic acid (EPA), are essential multifunctional nutrients in animals. Microorganisms such as microalgae are known to be n-3 LC-PUFA producers in aquatic environments. Various aquatic invertebrates, including Harpacticoida copepods, and a few terrestrial invertebrates, such as the nematode Caenorhabditis elegans, possess n-3 LC-PUFA biosynthetic enzymes. However, the capacity for n-3 LC-PUFA biosynthesis and the underlying molecular mechanisms in terrestrial insects are largely unclear. In this study, we investigated the fatty acid biosynthetic pathway in the silkworm Bombyx mori and found that EPA was present in silkworms throughout their development. Stable isotope tracing revealed that dietary α-linolenic acid (ALA) was metabolized to EPA in silkworm larvae. These results indicated that silkworms synthesize EPA from ALA. Given that EPA is enriched in the central nervous system, we propose that EPA confers optimal neuronal functions, similar to docosahexaenoic acid, in the mammalian nervous system.

COVID-19, caused by the novel coronavirus SARS-CoV-2, has presented a significant challenge to global health, security, and the economy. Vaccination is considered a crucial measure in preventing virus transmission. The silkworm bioreactor has gained widespread usage in antigen presentation, monoclonal antibody preparation, and subunit vaccine development due to its safety, efficiency, convenience, and cost-effectiveness. In this study, we employed silkworm BmN cells and the silkworm MultiBac multigene co-expression system to successfully produce two prototype vaccines: a recombinant baculovirus vector vaccine (NPV) co-displaying the SARS-CoV-2 virus capsid protein and a capsid protein virus-like particle (VLP) vaccine. Following the purification of these vaccines, we immunized BALB/c mice to evaluate their immunogenicity. Our results demonstrated that both VLP and NPV prototype vaccines effectively elicited robust immune responses in mice. However, when equal inoculation doses between groups were compared, the recombinant NPV vaccine exhibited significantly higher serum antibody titers and increased expression of spleen cytokines and lymphocyte immune regulatory factors compared to the VLP group. These results suggested an increased immune efficacy of the recombinant NPV vaccine. Conversely, the VLP prototype vaccine displayed more pronounced effects on lymphocyte cell differentiation induction. This study successfully constructed two distinct morphological recombinant vaccine models and systematically elucidated their differences in humoral immune response and lymphocyte differentiation rate. Furthermore, it has fully harnessed the immense potential of silkworm bioreactors for vaccine research and development, providing valuable technical insights for studying mutated viruses like coronaviruses.

Natural silks are renewable proteins with impressive mechanical properties and biocompatibility that are useful in various fields. However, the cellular and spatial organization of silk-secreting organs remains unclear. Here, we combined single-nucleus and spatially resolved transcriptomics to systematically map the cellular and spatial composition of the silk glands (SGs) of mulberry silkworms late in larval development. This approach allowed us to profile SG cell types and cell state dynamics and identify regulatory networks and cell-cell communication related to efficient silk protein synthesis; key markers were validated via transgenic approaches. Notably, we demonstrated the indispensable role of the ecdysone receptor (ultraspiracle) in regulating endoreplication in SG cells. Our atlas presents the results of spatiotemporal analysis of silk-secreting organ architecture late in larval development; this atlas provides a valuable reference for elucidating the mechanism of efficient silk protein synthesis and developing sustainable products made from natural silk.

Dengue virus (DENV) is a considerable public health threat affecting millions of people globally. Vaccines for dengue are an important strategy to reduce the disease burden. We expressed capsid (C2) and envelope domain III of dengue virus serotype 2 (2EDIII) separately in the silkworm expression system. We conjugated them employing the monomeric streptavidin (mSA2) and biotin affinity to display the antigenic 2EDIII on the C2-forming capsid-like particle (CLP). Purified 2EDIII-displaying C2 (CLP/2EDIII) was immunogenic in BALB/c mice, eliciting neutralizing antibodies confirmed by a single-round infectious particle (SRIP) neutralization assay. Th1 cytokine levels were upregulated for the CLP/2EDIII group, and the anti-inflammatory IL-10 and pro-inflammatory IL-6 cytokine levels were also raised compared to the 2EDIII and the control groups. Elevated cytokine levels for CLP/2EDIII indicate the importance of displaying the 2EDIII as CLP/2EDIII rather than as an individual subunit. This study is the first to express the C2 protein as self-assembling CLP in vivo and 2EDIII separately in the silkworm expression system and conjugate them to form a monovalent CLP. Thus, this CLP/2EDIII display method may pave the way for an efficient tetravalent dengue vaccine candidate.

Candida auris is an emerging pathogenic yeast that has been categorized as a global public health threat and a critical priority among fungal pathogens. Despite this, the immune response against C. auris infection is still not well understood. Hosts fight Candida infections through the immune system that recognizes pathogen-associated molecular patterns such as β-glucan, mannan, and chitin on the fungal cell wall. In this study, levels of β-glucan and mannan exposures in C. auris grown under different physiologically relevant stimuli were quantified by flow cytometry-based analysis. Lactate, hypoxia, and sublethal concentration of fluconazole trigger a decrease in surface β-glucan while low pH triggers an increase in β-glucan. There is no inverse pattern between exposure levels of β-glucan and mannan in the cell wall architecture among the three clades. To determine the effect of cell wall remodeling on the immune response, a phagocytosis assay was performed, followed by quantification of released cytokines by ELISA. Lactate-induced decrease in β-glucan leads to reduced uptake of C. auris by PMA-differentiated THP-1 and RAW 264.7 macrophages. Furthermore, reduced production of CCL3/MIP-1⍺ but not TNF-⍺ and IL-10 were observed. An in vivo infection analysis using silkworms reveals that a reduction in β-glucan triggers an increase in the virulence of C. auris. This study demonstrates that β-glucan alteration occurs in C. auris and serves as an escape mechanism from immune cells leading to increased virulence.