Amoeba Predation of Cryptococcus neoformans Results in Pleiotropic Changes to Traits Associated with Virulence.
Amoeba Predation of Cryptococcus neoformans Results in Pleiotropic Changes to Traits Associated with Virulence.
复制标题
新型隐球菌的阿米巴捕食导致与毒力相关的特征的多效性变化。
DOI：
10.1128/mbio.00567-21
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发表时间：
2021-04-27
期刊：
影响因子：
6.4
通讯作者：
Casadevall A
中科院分区：
文献类型：
--
作者：
Fu MS;Liporagi-Lopes LC;Dos Santos SR Júnior;Tenor JL;Perfect JR;Cuomo CA;Casadevall A
新生隐球菌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，特别是在免疫功能低下的患者中。该领域的一个主要问题是，当环境酵母(如新生葡萄球菌)在其生命周期中不需要动物宿主时，它如何成为人类病原体。阿米巴等变形虫捕食者被认为是土壤微生物如新生隐球菌的生存特征；这些特征也可以通过击败吞噬免疫细胞(如巨噬细胞)而在动物毒力中发挥作用。与这一观点一致的是，各种真菌物种与阿米巴孵育后，它们的毒力增强了，但涉及的机制尚不清楚。在这项研究中，我们将三株新生隐形杆菌(1株临床株和2株环境株)长期暴露在卡氏棘阿米巴的捕食下，并对存活的菌落进行了表型和遗传分析。存活的菌落由表达假菌丝或酵母表型的细胞组成，这些表型表现出与毒力相关的特征的不同表达，如被膜大小、尿素酶产生和黑化。在一些阿米巴传代分离株中，表型变化与非整倍体和DNA序列突变有关，而在另一些阿米巴传代分离株中则没有。在3株阿米巴传代分离株中均观察到寡肽转运蛋白(CNAG_03013；OPT1)基因突变。来自环境菌株的分离株在阿米巴选择后获得了增强巨噬细胞毒力的能力，并在编码AMP依赖的蛋白激酶调节因子(Pkr1)的CNAG_00570基因上发生突变，但在小鼠中表现出较低的毒力，因为它们诱导了更有效的真菌清除免疫反应。我们的结果表明，新生隐形杆菌在不断的阿米巴捕食下生存涉及到表达多效性表型和遗传变化的菌株的产生。考虑到土壤中有无数潜在的捕食者，在阿米巴选择的品系中观察到的多样性表明了一种更好的对冲策略，即变异多样性增加了一些变形虫在捕食中存活的可能性。
Cryptococcus neoformans 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 C. neoformans becomes a human pathogen when it has no need for an animal host in its life cycle. Amoeboid predators, such as amoebae, are proposed to select for survival traits in soil microbes such as Cryptococcus neoformans; 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 C. neoformans (1 clinical and 2 environmental) to predation by Acanthamoeba castellanii 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; OPT1) 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 C. neoformans 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.