The Evolution and Genetics of Fungal Virulence

项目总结 传染病的研究通常集中在病原微生物上，这些微生物要么专门利用 动物宿主或共生体，当宿主和宿主之间的微妙平衡切换到发病机制时 微生物被扰乱了。这些微生物被认为具有共同进化的复杂适应能力，从而使 在宿主体内和宿主上的生存和繁殖。然而，存在着广泛的微生物，它们生活在 在开放的环境中，当机会出现时，它们能够引发疾病。这样的微生物也 具有允许宿主利用的适应，但这些适应的来源尚不清楚，因为增长和 在宿主中生存并不是生命周期中必需的一部分。环境毒力性状的存在 派生的、机会性的病原体可能是由于选择有利于在非寄主中用于其他用途的特征所致 环境。这一假说在细菌文献中被称为“偶然选择”和“偶然选择”。 真菌文献中的“毒力”。新出现的细菌病原体的威胁受到了更多的关注 而不是真菌病原体的威胁。2022年，世界卫生组织发布了其有史以来第一份报告 优先考虑真菌病原体；前四名中有三名是环境真菌。因此，理解进化 对机会性病原体的控制是至关重要的。被“意外选择”的“两用”特征包括 多细胞(例如，生物膜形成、丝状生长、聚集)、保护性胶囊和毒素 制作。对这些性状的选择可以由非生物环境(例如温度)强制进行，但也可以 受到生物环境的影响。事实上，变形虫的捕食被认为是一种主要的选择力量。 支持两用特性并预先适应微生物以抵抗免疫系统中的吞噬细胞。这个 这里提出的研究将使用三种生物医学模型来研究两用之间的关系 特性、对阿米巴捕食的抵抗力和毒力。在目标1中，收集了1000个机会主义者的 芽酵母，酿酒酵母，将被调查的分布和遗传基础。 多细胞特征。为了评估对捕食的抵抗力，这些菌株还将受到 将对无脊椎动物模型进行阿米巴、盘基网柄菌和一个子集的毒力测试。 寄主，蜡蛾幼虫，斑潜蝇。AIMS 2和AIMS 3将专注于特定的临床酵母分离株。 首先，将通过一个图谱小组来探索这三个性状的遗传基础，以确定是否存在 这些性状之间有重叠的变异。然后，为了直接测试阿米巴捕食对真菌毒力的作用， 酵母和阿米巴将被共同培养和共同进化，以确定捕食是否选择增加 致命性。这项研究代表了最大的两用和抵抗捕食的表型筛选之一 机会主义真菌物种的相关特征，并将产生可用于 其他真菌种类。

PROJECT SUMMARY The study of infectious disease often focuses on pathogenic microbes that either specialize on exploiting animal hosts or on commensals that switch to pathogenesis when the delicate balance between host and microbe is perturbed. These microbes are presumed to have co-evolved complex adaptations that allow survival and reproduction in and on hosts. However, there exists a broad range of microbial organisms that live in the open environment that are capable of causing disease when the opportunity arises. Such microbes also have adaptations that allow host exploitation, but the origin of these adaptations is unclear, as growth and survival in a host is not a required part of the lifecycle. The existence of virulence traits in environmentally- derived, opportunistic pathogens is likely due to selection favoring the traits for other uses in the non-host environment. This hypothesis is known as “coincidental selection” in the bacterial literature, and “accidental virulence” in the fungal literature. The threat of emerging bacterial pathogens has received far more attention than the threat of fungal pathogens. In 2022, the World Health Organization issued its first-ever report prioritizing fungal pathogens; three of the top four were environmental fungi. Thus, understanding the evolution of opportunistic pathogens is essential. Examples of ‘dual-use’ traits that are “accidentally selected” include multicellularity (e.g., biofilm formation, filamentous growth, aggregation), protective capsules, and toxin production. Selection for these traits can be imposed by the abiotic environment (e.g., temperature), but also by the biotic environment. Indeed, amoeba predation has been hypothesized to be a major selective force favoring dual-use traits and preadapting microbes to be resistant to phagocytes in the immune system. The research proposed here will use three biomedical models to investigate the relationship between dual-use traits, resistance to amoeba predation, and virulence. In Aim 1, a collection of 1000 isolates of the opportunistic budding yeast, Saccharomyces cerevisiae, will be investigated for the distribution and genetic basis of multicellular traits. To estimate predation resistance, the strains will also be subject to phagocytosis by the amoeba, Dictyostelium discoideum, and a subset will be tested for virulence against the invertebrate model host, larvae of the wax moth, Galleria mellonella. Aims 2 and 3 will focus on specific clinical yeast isolates. First, the genetic basis of the three traits will be explored with a mapping panel to determine whether there are overlapping variants among the traits. Then, to directly test the role of amoeba predation on fungal virulence, the yeast and amoeba will be co-cultured and co-evolved to determine whether predation selects for increased virulence. This research represents one of the largest phenotypic screens of dual-use and predation-resistance related traits in an opportunistic fungal species, and will generate experimental techniques that may be used in other fungal species.