PDF(Pubmed)
Abstract：
Histoplasmosis is an endemic mycosis that often presents as a respiratory infection in immunocompromised patients. Hundreds of thousands of new infections are reported annually around the world. The etiological agent of the disease, Histoplasma, is a dimorphic fungus commonly found in the soil where it grows as mycelia. Humans can become infected by Histoplasma through inhalation of its spores (conidia) or mycelial particles. The fungi transition into the yeast phase in the lungs at 37°C. Once in the lungs, yeast cells reside and proliferate inside alveolar macrophages. Genomic work has revealed that Histoplasma is composed of at least five cryptic phylogenetic species that differ genetically. Three of those lineages have received new names. Here, we evaluated multiple phenotypic characteristics (colony morphology, secreted proteolytic activity, yeast size, and growth rate) of strains from five of the phylogenetic species of Histoplasma to identify phenotypic traits that differentiate between these species: Histoplasma capsulatum sensu stricto, Histoplasma ohiense, Histoplasma mississippiense, Histoplasma suramericanum, and an African lineage. We report diagnostic traits for three species. The other two species can be identified by a combination of traits. Our results suggest that (i) there are significant phenotypic differences among the cryptic species of Histoplasma and (ii) those differences can be used to positively distinguish those species in a clinical setting and for further study of the evolution of this fungal pathogen.IMPORTANCEIdentifying species boundaries is a critical component of evolutionary biology. Genome sequencing and the use of molecular markers have advanced our understanding of the evolutionary history of fungal pathogens, including Histoplasma, and have allowed for the identification of new species. This is especially important in organisms where morphological characteristics have not been detected. In this study, we revised the taxonomic status of the four named species of the genus Histoplasma, H. capsulatum sensu stricto (ss), H. ohiense, H. mississippiense, and H. suramericanum, and propose the use of species-specific phenotypic traits to aid their identification when genome sequencing is not available. These results have implications not only for evolutionary study of Histoplasma but also for clinicians, as the Histoplasma species could determine the outcome of disease and treatment needed.
摘要：
组织胞浆菌病是一种地方性真菌病，通常在免疫功能低下的患者中表现为呼吸道感染。全世界每年报告成千上万的新感染。疾病的病因，组织胞浆,是一种双态真菌，通常在它以菌丝体生长的土壤中发现。人类可以通过吸入其孢子（分生孢子）或菌丝体颗粒而被组织胞浆感染。真菌在37°C时在肺中转变为酵母相。一旦进入肺部，酵母细胞在肺泡巨噬细胞内驻留和增殖。基因组工作表明，组织胞浆由至少五个遗传上不同的隐秘系统发育物种组成。其中三个血统获得了新名称。这里,我们评估了多种表型特征(菌落形态，分泌的蛋白水解活性，酵母大小，和生长速率）来自五个组织胞浆系统发育物种的菌株，以鉴定区分这些物种的表型性状：严格的荚膜组织胞浆，Ohiense组织胞浆，Missippiense组织支原体，suramericanum,和非洲血统。我们报告了三个物种的诊断特征。另外两个物种可以通过性状的组合来鉴定。我们的结果表明（i）组织胞浆的隐匿性物种之间存在显着的表型差异，并且（ii）这些差异可用于在临床环境中积极区分这些物种，并进一步研究这种真菌病原体的进化。重要意义识别物种边界是进化生物学的重要组成部分。基因组测序和分子标记的使用促进了我们对真菌病原体进化史的理解，包括组织支原体,并允许识别新物种。这在尚未检测到形态特征的生物体中尤其重要。在这项研究中,我们修改了四个命名物种的分类地位，H.严格的囊膜（SS），H.ohiense,H.密西西比州，和H.suramericanum，并建议在无法进行基因组测序时使用物种特异性表型性状来帮助鉴定它们。这些结果不仅对组织胞浆的进化研究有意义，而且对临床医生也有意义。因为组织胞浆物种可以决定疾病的结果和所需的治疗。
