Pathogenic Potential (PP) is a mathematical description of an individual microbe, virus, or parasite's ability to cause disease in a host, given the variables of inoculum, signs of disease, ...mortality, and in some instances, median survival time of the host. We investigated the relationship between pathogenic potential (PP) and infective inoculum (I) using two pathogenic fungi in the wax moth Galleria mellonella with mortality as the relevant outcome. Our analysis for C. neoformans infection revealed negative exponential relationship between PP and I. Plotting the log(I) versus the Fraction of animals with signs or symptoms (Fs) over median host survival time (T) revealed a linear relationship, with a slope that varied between the different fungi studied and a y-intercept corresponding to the inoculum that produced no signs of disease. The I vs Fs/T slope provided a measure of the pathogenicity of each microbial species, which we call the pathogenicity constant or kPath. The kPath provides a new parameter to quantitatively compare the relative virulence and pathogenicity of microbial species for a given host. In addition, we investigated the PP and Fs/T from values found in preexisting literature. Overall, the relationship between Fs/T and PP versus inoculum varied among microbial species and extrapolation to zero signs of disease allowed the calculation of the lowest pathogenic inoculum (LPI) of a microbe. Microbes tended to fall into two groups: those with positive linear relationships between PP and Fs/T vs I, and those that had a negative exponential PP vs I relationship with a positive logarithmic Fs/T vs I relationship. The microbes with linear relationships tended to be bacteria, whereas the exponential-based relationships tended to be fungi or higher order eukaryotes. Differences in the type and sign of the PP vs I and Fs/T vs I relationships for pathogenic microbes suggest fundamental differences in host-microbe interactions leading to disease.
ABSTRACT
In recent decades, Galleria mellonella (Lepidoptera: Pyralidae) have emerged as a model system to explore experimental aspects of fungal pathogenesis. The benefits of the G. mellonella model ...include being faster, cheaper, higher throughput and easier compared with vertebrate models. Additionally, as invertebrates, their use is subject to fewer ethical and regulatory issues. However, for G. mellonella models to provide meaningful insight into fungal pathogenesis, the G. mellonella–fungal interactions must be comparable to mammalian–fungal interactions. Indeed, as discussed in the review, studies suggest that G. mellonella and mammalian immune systems share many similarities, and fungal virulence factors show conserved functions in both hosts. While the moth model has opened novel research areas, many comparisons are superficial and leave large gaps of knowledge that need to be addressed concerning specific mechanisms underlying G. mellonella–fungal interactions. Closing these gaps in understanding will strengthen G. mellonella as a model for fungal virulence in the upcoming years. In this review, we provide comprehensive comparisons between fungal pathogenesis in mammals and G. mellonella from immunological and virulence perspectives. When information on an antifungal immune component is unknown in G. mellonella, we include findings from other well-studied Lepidoptera. We hope that by outlining this information available in related species, we highlight areas of needed research and provide a framework for understanding G. mellonella immunity and fungal interactions.
Galleria mellonella is a useful model for studying fungal infections with Galleria sharing many similarities with mammals' antifungal immune system and interactions with fungal virulence factors.
Melanin, a black-brown pigment found throughout all kingdoms of life, has diverse biological functions including UV protection, thermoregulation, oxidant scavenging, arthropod immunity, and microbial ...virulence. Given melanin's broad roles in the biosphere, particularly in insect immune defenses, it is important to understand how exposure to ubiquitous environmental contaminants affects melanization. Glyphosate-the most widely used herbicide globally-inhibits melanin production, which could have wide-ranging implications in the health of many organisms, including insects. Here, we demonstrate that glyphosate has deleterious effects on insect health in 2 evolutionary distant species, Galleria mellonella (Lepidoptera: Pyralidae) and Anopheles gambiae (Diptera: Culicidae), suggesting a broad effect in insects. Glyphosate reduced survival of G. mellonella caterpillars following infection with the fungus Cryptococcus neoformans and decreased the size of melanized nodules formed in hemolymph, which normally help eliminate infection. Glyphosate also increased the burden of the malaria-causing parasite Plasmodium falciparum in A. gambiae mosquitoes, altered uninfected mosquito survival, and perturbed the microbial composition of adult mosquito midguts. Our results show that glyphosate's mechanism of melanin inhibition involves antioxidant synergy and disruption of the reaction oxidation-reduction balance. Overall, these findings suggest that glyphosate's environmental accumulation could render insects more susceptible to microbial pathogens due to melanin inhibition, immune impairment, and perturbations in microbiota composition, potentially contributing to declines in insect populations.
Disaster mycology Smith, Daniel F Q; Casadevall, Arturo
Biomedica : revista del Instituto Nacional de Salud,
08/2023, Letnik:
43, Številka:
Sp. 1
Journal Article
Recenzirano
Odprti dostop
Natural and human-made disasters have long played a role in shaping the environment and microbial communities, also affecting non-microbial life on Earth. Disaster microbiology is a new concept based ...on the notion that a disaster changes the environment causing adaptation or alteration of microbial populations -growth, death, transportation to a new area, development traits, or resistance- that can have downstream effects on the affected ecosystem. Such downstream effects include blooms of microbial populations and the ability to colonize a new niche or host, cause disease, or survive in former extreme conditions. Throughout history, fungal populations have been affected by disasters. There are prehistoric archeological records of fungal blooms after asteroid impacts and fungi implicated in the fall of the dinosaurs. In recent times, drought and dust storms have caused disturbance of soil fungi, and hurricanes have induced the growth of molds on wet surfaces, resulting in an increased incidence of fungal disease. Probably, the anticipated increase in extreme heat would force fungi adaptation to survive at high temperatures, like those in the human body, and thus be able to infect mammals. This may lead to a drastic rise of new fungal diseases in humans.
Natural and human-made disasters can cause tremendous physical damage, societal change, and suffering. In addition to their effects on people, disasters have been shown to alter the microbial ...population in the area affected. Alterations for microbial populations can lead to new ecological interactions, with additional potentially adverse consequences for many species, including humans. Disaster-related stressors can be powerful forces for microbial selection. Studying microbial adaptation in disaster sites can reveal new biological processes, including mechanisms by which some microbes could become pathogenic and others could become beneficial (e.g., used for bioremediation). Here we survey examples of how disasters have affected microbiology and suggest that the topic of "disaster microbiology" is itself a new field of study. Given the accelerating pace of human-caused climate change and the increasing encroachment of the natural word by human activities, it is likely that this area of research will become increasingly relevant to the broader field of microbiology. Since disaster microbiology is a broad term open to interpretation, we propose criteria for what phenomena fall under its scope. The basic premise is that there must be a disaster that causes a change in the environment, which then causes an alteration to microbes (either a physical or biological adaptation), and that this adaptation must have additional ramifications.
Outer membrane vesicles produced by Gram-negative bacteria have been studied for half a century but the possibility that Gram-positive bacteria secrete extracellular vesicles (EVs) was not pursued ...until recently due to the assumption that the thick peptidoglycan cell wall would prevent their release to the environment. However, following their discovery in fungi, which also have cell walls, EVs have now been described for a variety of Gram-positive bacteria. EVs purified from Gram-positive bacteria are implicated in virulence, toxin release, and transference to host cells, eliciting immune responses, and spread of antibiotic resistance. Listeria monocytogenes is a Gram-positive bacterium that causes listeriosis. Here we report that L. monocytogenes produces EVs with diameters ranging from 20 to 200 nm, containing the pore-forming toxin listeriolysin O (LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC). Cell-free EV preparations were toxic to mammalian cells, the murine macrophage cell line J774.16, in a LLO-dependent manner, evidencing EV biological activity. The deletion of plcA increased EV toxicity, suggesting PI-PLC reduced LLO activity. Using simultaneous metabolite, protein, and lipid extraction (MPLEx) multiomics we characterized protein, lipid, and metabolite composition of bacterial cells and secreted EVs and found that EVs carry the majority of listerial virulence proteins. Using immunogold EM we detected LLO at several organelles within infected human epithelial cells and with high-resolution fluorescence imaging we show that dynamic lipid structures are released from L. monocytogenes during infection. Our findings demonstrate that L. monocytogenes uses EVs for toxin release and implicate these structures in mammalian cytotoxicity.
A key component of the insect immune response is melanin production, including within nodules, or aggregations of immune cells surrounding microbes. Melanization produces oxidative and toxic ...intermediates that limit microbial infections. However, a direct fungicidal role of melanin during infection has not been demonstrated. We previously reported that the fungus Cryptococcus neoformans is encapsulated with melanin within nodules of Galleria mellonella hosts. Here we developed techniques to study melanin's role during C. neoformans infection in G. mellonella. We provided evidence that in vivo melanin-encapsulation was fungicidal. To further study immune melanization, we applied tissue-clearing techniques to visualize melanized nodules in situ throughout the larvae. Further, we developed a time-lapse microscopy protocol to visualize the melanization kinetics in extracted hemolymph following fungal exposure. Using this technique, we found that cryptococcal melanin and laccase enhance immune melanization. We extended this approach to study the fungal pathogens Candida albicans and Candida auris. We find that the yeast morphologies of these fungi elicited robust melanization responses, while hyphal and pseudohyphal morphologies were melanin-evasive. Approximately 23% of melanin-encapsulated C. albicans yeast can survive and breakthrough the encapsulation. Overall, our results provide direct evidence that immune melanization functions as a direct antifungal mechanism in G. mellonella.
Classic antibody functions include opsonization, complement activation, and enhancement of cellular antimicrobial function. Antibodies can also have catalytic activity, although the contribution of ...catalysis to their biological functions has been more difficult to establish. With the ubiquity of catalytic antibodies against glycans virtually unknown, we sought to advance this knowledge. The use of a glycan microarray allowed epitope mapping of several monoclonal antibodies (mAbs) against the capsule of
From this, we designed and synthesized two glycan-based FRET probes, which we used to discover antibodies with innate glycosidase activity and analyze their enzyme kinetics, including mAb 2H1, the most efficient identified to date. The validity of the FRET assay was confirmed by demonstrating that the mAbs mediate glycosidase activity on intact cryptococcal capsules, as observed by a reduction in capsule diameter. Furthermore, the mAb 18B7, a glycosidase hydrolase, resulted in the appearance of reducing ends in the capsule as labeled by a hydroxylamine-armed fluorescent (HAAF) probe. Finally, we demonstrate that exposing
cells to catalytic antibodies results in changes in complement deposition and increased phagocytosis by macrophages, suggesting that the antiphagocytic properties of the capsule have been impaired. Our results raise questions over the ubiquity of antibodies with catalytic activity against glycans and establish the utility of glycan-based FRET and HAAF probes as tools for investigating this activity.
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