Malassezia species are part of human commensal microbiota and is also related to diseases. Little is known about the interaction of these microorganisms with their host. Here we established two standard culture conditions for Malassezia spp. to perform infection assays using C. elegans and T. molitor. Invertebrate hosts infected by Malassezia spp. cultured in M9M resulted in higher death rate on survival assays when compared to yeasts cultured in standard Dixon medium indicating that M9M cultured Malassezia species have increased virulence. The culture and infection conditions established in this work, using invertebrate alternative models, are valuable tools to understand Malassezia-host interaction.

Deoxynivalenol (DON) is a mycotoxin produced by Fusarium spp. that causes Fusarium head blight (FHB) disease in cereal crops. Ingestion of food contaminated with DON poses serious human health complications. However, the DON cytotoxicity has been mostly deduced from animal studies. In this study, we used the nematode Caenorhabditis elegans (C. elegans) as a tractable animal model to dissect the toxic effect of DON. Our results indicate that DON reduces the fecundity and lifespan of C. elegans. The real-time RT-PCR analysis showed that DON upregulates innate immunity-related genes including C17H12.8 and K08D8.5 encoding PMK-1 (mitogen activated protein kinase-1)-regulated immune effectors, and F35E12.5 encoding a CUB-like domain-containing protein. Furthermore, our RNAseq data demonstrate that out of ~ 17,000 C. elegans genes, 313 are upregulated and 166 were downregulated by DON treatment. Among the DON-upregulated genes, several are ugt genes encoding UDP-glucuronosyl transferase (UGTs) which are known to be involved in chemical detoxification. The three upregulated genes, F52F10.4 (oac-32), C10H11.6 (ugt-26) and C10H11.4 (ugt-28) encoding the O-acyltransferase homolog, UGT26 and UGT 28, respectively, are shown to contribute to DON tolerance by RNAi bacterial feeding experiment. The results of this study provide insights to the targets of DON cytotoxicity and potential mitigation measures.

Background The nematode Caenorhabditis elegans (C. elegans) possesses a sophisticated sense of smell and is used for a novel cancer screening test that utilizes the chemotaxis index. We designed a single-institution, prospective study to confirm the ability of Nematode Nose (N-NOSE) to determine preoperative chemotherapy's efficacy for esophageal cancer patients. Patients and Methods We investigated the predictability of N-NOSE screening for the clinical effects of preoperative chemotherapy for esophageal cancer patients receiving radical surgery. The index reduction score (IRS) was calculated by chemotaxis of C. elegans at three points: before treatment, before surgery, and after surgery, and its clinical relevance was examined. Result Thirty-nine patients with esophageal cancer were enrolled from August 2020 to December 2021 and 30 patients receiving radical surgery were examined. Complete response or partial response was achieved in 23 cases (76.7%). When the target of the treatment effect was complete response only, the prediction accuracies of the IRS calculated by area under the curve was 0.85 (95% Confidence interval: 0.62-1) in clinically achieving complete response group, and the sensitivity and specificity were 1 and 0.63, respectively. Conclusion Index reduction score using N-NOSE screening may reflect the efficacy of chemotherapy for esophageal cancer patients. A large-scale prospective study at multiple centers is desired in the future.

The lectin found in the tubers of the Winter Aconite (Eranthis hyemalis) plant (EHL) is a Type II Ribosome Inactivating Protein (RIP); type II RIPs have shown anti-cancer properties, and have great potential as therapeutic agents. Similarly, colloidal gold nanoparticles are successfully used in biomedical applications as gold nanoparticles can be functionalised with ligands with high affinity and specificity for target cells to create therapeutic and imaging agents. Herein we present the synthesis and characterization of gold nanoparticles conjugated with EHL. The aim was to establish the viability of the conjugate and perform a set of initial assays to establish whether the biological effect of EHL is altered by the conjugation. The biological assays were performed in Caenorhabditis elegans, a free living nematode commonly used for toxicological studies; previous work from some of the authors using first life stage (L1) nematodes has shown that EHL has a strong biocidal effect on C. elegans. Gold nanoparticles functionalised with EHL (AuNPs@EHL) were successfully synthesised by bioconjugation with citrate gold nanoparticles (AuNPs@Citrate); the conjugates were analysed by UV-Vis spectroscopy, Dynamic Light Scattering (DLS), Zeta Potential analysis and Transmission Electron Microscopy (TEM). Results indicate that an optimal functionalisation was achieved with the addition of 100 µL of EHL (concentration 1090 ± 40 µg/mL) over 5 mL of AuNPs (concentration [Au0] = 0.8 mM). Biological assays on the effect of AuNPs@EHL on C. elegans were performed, using first life stage (L1) and pre-adult stage (L4) nematodes. Citrate gold nanoparticles did not have any obvious effect on the nematodes. For L1 stage nematodes, the assays show that conjugation with gold nanoparticles reduced the biological effect of EHL on C. elegans. As lectin binding activity is essential for the natural protein to bind and allow entry to cells, conformational changes due to conjugation may have affected this binding affinity. For L4 stage nematodes, both EHL alone and AuNPs@EHL showed biological activity, and reproductive delays and reduced fecundity were observed in both cases. These assays indicate that EHL can be conjugated to gold nanoparticles and retain elements of biocidal activity.

Since the discovery of transposable elements (TEs) in Maize in the 1940s by Barbara McClintock [1] transposable elements have been described as junk, as selfish elements with no benefit to the host, and more recently as major determinants of genome structure and genome evolution. TEs are DNA sequences that are capable of moving to new sites in the genome and make additional copies while doing so. To limit the propagation of TEs, host silencing mechanisms are directed at transposon-encoded genes that are required for mobilization. The mutagenic properties of TEs, the potential of TEs to form new genes and affect gene expression, together with the host silencing mechanisms shape eukaryotic genomes and drive genome evolution. While TEs constitute more than half of the genome in many higher eukaryotes, transposable elements in the nematode C. ele-gans form a relatively small proportion of genome, about 15% [2]. Genetic studies of transposon silencing and the discovery of RNAi in C. elegans, propelled C. elegans to the forefront of studies of RNA-based mechanisms that silence TEs. Here, I will review the transposable elements that are present and active in the C. elegans genome, and the host defense mechanisms that silence these elements.

The conventional phytopathogen Pseudomonas syringae has been identified several significant virulence determinants against Caenorhabditis elegans, but their mechanisms of action remain elusive. Here, we report the nematicidal activity and action receptor of a methyl-accepting chemotaxis protein (MCP03) of a wild-type P. syringae MB03 against C. elegans. Purified MCP03 exhibited significant nematicidal toxicity against C. elegans, with a half-lethal concentration of 124.4 μg mL1, and detrimental effects on the growth and brood size of C. elegans. Additionally, MCP03-treated worms showed severe pathological destruction of the intestine and ovary, and depressed wrinkles of the cuticle. Through yeast two-hybrid assays, we identified a subunit of a COP9 signalosome, namely CSN-5, functionated as an action receptor of MCP03. In vitro pull-down and in vivo co-localization assays verified the binding interaction between MCP03 and CSN-5. RNA interference assays confirmed that MCP03 acts on CSN-5 to adversely affect the brood size, growth, and cuticle integrity of C. elegans. Following MCP03 infection, the expression of several genes relative to reproduction, growth, and cuticle formation, such as kgb-1, unc-98, and col-117, were significantly downregulated, which implicated the pathological changes of MCP03-treated nematodes. Thus, this study demonstrates that MCP03 acted on the receptor protein CSN-5 causing lethality and detrimental effects on the fertility, growth, and morphogenesis of C. elegans, which will provide new insights into the signaling pathways and mechanism underlying the nematicidal action of MCP03 towards C. elegans.

Neurodegenerative protein conformational diseases are characterized by misfolding and aggregation of metastable proteins encoded within the host genome. The host is also home to thousands of proteins encoded within exogenous genomes harbored by bacteria, fungi, and viruses. Yet, their contributions to host protein-folding homeostasis, or proteostasis, remain elusive. Recent studies, including our previous work, suggest that bacterial products contribute to toxic aggregation of endogenous host proteins. We refer to these products as bacteria-derived protein aggregates (BDPAs). Furthermore, antibiotics were recently associated with increased risk for neurodegenerative diseases, including Parkinson’s disease and amyotrophic lateral sclerosis  possibly by virtue of altering the composition of the human gut microbiota. Other studies have shown a negative correlation between disease progression and antibiotic administration, supporting their protective effect against neurodegenerative diseases. These contradicting studies emphasize the complexity of the human gut microbiota, the gut-brain axis, and the effect of antibiotics. Here, we further our understanding of bacteria’s effect on host protein folding using the model Caenorhabditis elegans. We employed genetic and chemical methods to demonstrate that the proteotoxic effect of bacteria on host protein folding correlates with the presence of BDPAs. Furthermore, the abundance and proteotoxicity of BDPAs are influenced by gentamicin, an aminoglycoside antibiotic that induces protein misfolding, and by butyrate, a short-chain fatty acid that we previously found to affect host protein aggregation and the associated toxicity. Collectively, these results increase our understanding of host-bacteria interactions in the context of protein conformational diseases.

Whole genome duplication (WGD) or polyploidization can occur at the cellular, tissue, and organismal levels. At the cellular level, tetraploidization has been proposed as a driver of aneuploidy and genome instability, and correlates strongly with cancer progression, metastasis, and development of drugs resistance[1–6]. WGD is also a key developmental strategy for regulating cell size, metabolism, and cellular function[1,7–10]. In specific tissues, WGD is involved in normal development (e.g. organogenesis), tissue homeostasis, wound healing, and regeneration[10–17]. At the organismal level, WGD propels evolutionary processes such as adaptation[18], speciation[19], and crop domestication[20]. An essential strategy to further our understanding of the mechanisms promoting WGD and its effects is to compare isogenic strains that differ only in their ploidy. Caenorhabditis elegans (C. elegans) is emerging as an animal model for these comparisons, in part because relatively stable and fertile tetraploid strains can be produced rapidly from nearly any diploid strain[7]. Here we review the use of Caenorhabditis polyploids as tools to understand important developmental processes (e.g. sex determination, dosage compensation, and allometric relationships)[21–27] and cellular processes (e.g. cell cycle regulation, chromosome dynamics during meiosis)[28–32]. We also discuss how the unique characteristics of the C. elegans WGD model will enable significant advances in our understanding of mechanisms of polyploidization and its role in development and disease.