变形虫对新型隐球菌的捕食导致与毒力相关的性状发生多效变化。

Amoeba Predation of Cryptococcus neoformans Results in Pleiotropic Changes to Traits Associated with Virulence.

机构信息

Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.

Departamento de Análises Clínicas e Toxicológicas, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.

出版信息

mBio. 2021 Apr 27;12(2):e00567-21. doi: 10.1128/mBio.00567-21.

Abstract

Amoeboid predators, such as amoebae, are proposed to select for survival traits in soil microbes such as ; these traits can also function in animal virulence by defeating phagocytic immune cells, such as macrophages. Consistent with this notion, incubation of various fungal species with amoebae enhanced their virulence, but the mechanisms involved are unknown. In this study, we exposed three strains of (1 clinical and 2 environmental) to predation by for prolonged times and then analyzed surviving colonies phenotypically and genetically. Surviving colonies comprised cells that expressed either pseudohyphal or yeast phenotypes, which demonstrated variable expression of traits associated with virulence, such as capsule size, urease production, and melanization. Phenotypic changes were associated with aneuploidy and DNA sequence mutations in some amoeba-passaged isolates, but not in others. Mutations in the gene encoding the oligopeptide transporter (CNAG_03013; ) were observed among amoeba-passaged isolates from each of the three strains. Isolates derived from environmental strains gained the capacity for enhanced macrophage toxicity after amoeba selection and carried mutations on the CNAG_00570 gene encoding Pkr1 (AMP-dependent protein kinase regulator) but manifested reduced virulence in mice because they elicited more effective fungal-clearing immune responses. Our results indicate that survival under constant amoeba predation involves the generation of strains expressing pleiotropic phenotypic and genetic changes. Given the myriad potential predators in soils, the diversity observed among amoeba-selected strains suggests a bet-hedging strategy whereby variant diversity increases the likelihood that some will survive predation. is a ubiquitous environmental fungus that is also a leading cause of fatal fungal infection in humans, especially among immunocompromised patients. A major question in the field is how an environmental yeast such as becomes a human pathogen when it has no need for an animal host in its life cycle. Previous studies showed that increases its pathogenicity after interacting with its environmental predator amoebae. Amoebae, like macrophages, are phagocytic cells that are considered an environmental training ground for pathogens to resist macrophages, but the mechanism by which changes its virulence through interactions with protozoa is unknown. Our study indicates that fungal survival in the face of amoeba predation is associated with the emergence of pleiotropic phenotypic and genomic changes that increase the chance of fungal survival, with this diversity suggesting a bet-hedging strategy to ensure that some forms survive.

摘要

变形虫状捕食者,如变形虫,被认为可以选择土壤微生物中的生存特征;这些特征也可以通过击败吞噬免疫细胞(如巨噬细胞)在动物毒力中发挥作用。与这一观点一致的是,用变形虫孵育各种真菌物种可以增强它们的毒力,但涉及的机制尚不清楚。在这项研究中,我们将三种 (1 种临床和 2 种环境)菌株暴露于变形虫捕食下很长时间,然后从表型和遗传上分析存活的菌落。存活的菌落由表达假菌丝或酵母表型的细胞组成,这些细胞表现出与毒力相关的特征的可变表达,如荚膜大小、脲酶产生和黑色素化。表型变化与一些经过变形虫传递的分离株中的非整倍体和 DNA 序列突变有关,但在其他分离株中则没有。在来自三种菌株的经过变形虫传递的分离株中观察到编码寡肽转运体(CNAG_03013;)的基因发生突变。从环境菌株获得的分离株在经过变形虫选择后获得了增强巨噬细胞毒性的能力,并在编码 Pkr1(AMP 依赖性蛋白激酶调节剂)的 CNAG_00570 基因上携带突变,但在小鼠中表现出降低的毒力,因为它们引发了更有效的真菌清除免疫反应。我们的结果表明,在持续的变形虫捕食下的 生存涉及到表达多效性表型和遗传变化的菌株的产生。鉴于土壤中存在无数潜在的捕食者,在经过变形虫选择的菌株中观察到的多样性表明了一种赌注分散策略,即变体多样性增加了一些菌株在捕食下幸存的可能性。 是一种普遍存在的环境真菌,也是人类致命真菌感染的主要原因,尤其是在免疫功能低下的患者中。该领域的一个主要问题是,作为一种环境酵母, 如何在其生命周期中不需要动物宿主的情况下成为人类病原体。先前的研究表明, 与环境捕食者变形虫相互作用后,其致病性会增加。变形虫与巨噬细胞一样,都是吞噬细胞,被认为是病原体抵抗巨噬细胞的环境训练场,但 如何通过与原生动物相互作用改变其毒力的机制尚不清楚。我们的研究表明,真菌在面对变形虫捕食时的生存与多效性表型和基因组变化的出现有关,这些变化增加了真菌生存的机会,这种多样性表明了一种赌注分散策略,以确保一些形式的生存。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/a352/8092252/e6396f024279/mBio.00567-21-f001.jpg

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