Phenotypic Plasticity and Inter-Species Communication in Candida Albicans

描述（由申请方提供）：致病性酵母菌白色念珠菌是人类植物群的主要组成部分，具有可塑性，使其既能作为一种寄生生物，也能作为一种威胁生命的病原体茁壮成长。90%的HIV感染者会发生口咽念珠菌病（OPC），5%的新生儿和10%的老年患者也会发生口腔念珠菌感染（2; 3）。这种真菌变色龙通过对外界信号的反应来调节形态、表型和菌落结构的变化，这些变化赋予了C。白念珠菌具有增加其毒力、增强定植、允许交流和抵抗抗真菌药物的特性。本提案中包含的实验解决了这种可塑性的关键特征，这些特征对C。白色念珠菌致病性：环境信号和种间通信如何激发表型转换和信息素信号传导途径，这两者都是直接参与生物膜形成的过程。我的初步工作表明，在氧化应激和常用的抗真菌药物氟胞嘧啶的存在下，调节生物膜形成和交配的白色不透明开关增加。有了这些结果，在我的第一个目标中，我将确定C语言中的转换率。白念珠菌对氧化应激、亚硝化应激和抗真菌药物暴露的反应。这些因素是C.白色念珠菌在临床环境中，因此，将分析几种临床分离株。我还将确定它们增加表型转换的反应途径。我假设涉及硫氧还蛋白途径和Rad 53途径，因此将使用TRX 1、TRR 1、CAP 1和Rad 53的基因缺失和过表达菌株对其进行测试。 我的第二个目标是解决白色念珠菌与人类口腔微生物组的真菌和细菌成员之间的种间事件。本实验室的结果表明，来自其他念珠菌属的信息素信号可诱导念珠菌形成生物膜。白色念珠菌，我将进一步研究这一目标（14）。首先，我将使用一组C.我构建的白色念珠菌菌株分泌这些其他物种的信息素来代替自己的。我预计我的实验将表明，交配和生物膜的形成都发生在响应信号通过几个念珠菌物种的信息素，涉及真菌间的信号在发病机制。此外，我将直接共培养C。白色念珠菌伴已知细菌 口腔微生物组的成员，包括分泌高水平过氧化氢的戈登链球菌，这是一种已知的应激源和转换诱导物（43）。我的第二个目标的结果将得到我的第一个目标的支持。 了解白色不透明开关和物种间信号传导事件将允许开发新的治疗方法，用于预防与这种真菌病原体相关的通常使人衰弱，有时甚至致命的感染。 公共卫生相关性：白色念珠菌是人类植物群的重要组成部分，既作为寄生菌又作为致病菌存在，利用表型的变化逃避宿主免疫系统应答并栖息于不同的生态位。这个建议将测试C。白念珠菌向不透明表型转变，这对于成功感染是重要的，以及种间信号传导对白念珠菌的影响。白色念珠菌定殖和生物膜形成。这些因素是C.白色念珠菌能够引起口腔和阴道鹅口疮、义齿性口炎和全身感染，尤其是在免疫受损的个体中。

DESCRIPTION (provided by applicant): The pathogenic yeast, Candida albicans is a major constituent of the human flora with a plasticity that allows it to thrive both as a commensal organism and as a life-threatening pathogen. 90% of HIV-infected individuals develop oropharyngeal candidiasis (OPC), and oral Candida infections also affect 5% of newborns and 10% of elderly patients (2; 3). This fungal chameleon mediates changes in morphology, phenotype, and colony structure by responding to external cues, and these alterations endow C. albicans with traits that increase its virulence, enhance colonization, allow communication and resist anti-fungal drugs. The experiments contained in this proposal address key features of this plasticity that are paramount to C. albicans pathogenicity: how environmental signals and inter-species communication instigate phenotypic switching and pheromone signaling pathways, both of which are processes directly implicated in biofilm formation. My preliminary work shows that the white-opaque switch, which regulates both biofilm formation and mating, is increased in the presence of oxidative stress and also the commonly used anti-fungal drug Flucytosine. Given these results, in my first aim I will determine the rates of switching in C. albicans in response t oxidative stress, nitrosative stress and anti-fungal drug exposure. These factors are common challenges to C. albicans in the clinical setting, and as such, several clinical isolates will be analyzed. I will also identify the response pathway by which they increase phenotypic switching. I hypothesize that the thioredoxin pathway and Rad53 pathways are involved, so they will be tested using gene deletion and over-expression strains for TRX1, TRR1, CAP1, and RAD53. My second aim will address inter-species events between Candida albicans and the fungal and bacterial members of the human oral microbiome. Results from my laboratory shows that pheromone signals from other Candida species induce biofilm formation by C. albicans, which I will further investigate in this aim (14). First, I will determine if signaling between Candida species occurs at physiologically-relevant pheromone concentrations using a set of C. albicans strains I have constructed that secrete pheromones native to these other species in place of its own. I anticipate that my experiments will show that both mating and biofilm formation occur in response to signaling via several Candida species' pheromones, implicating inter-fungal signaling in pathogenesis. Furthermore, I will directly co-culture C. albicans with known bacterial members of the oral microbiome, including Streptococcus gordonii, which secretes high levels of hydrogen peroxide, a known stressor and switch inducer (43). Such results from my second aim will be supported by my first aim. Understanding the white-opaque switch and inter-species signaling events will allow the development of new treatments for preventing the often debilitating, and sometimes even fatal, infections associated with this fungal pathogen. PUBLIC HEALTH RELEVANCE: Candida albicans is an important part of the human flora, existing as both a commensal and pathogenic species, using changes in phenotype to evade host immune system responses and inhabit diverse niches. This proposal will test how C. albicans transitions to the opaque phenotype, which is important to successful infection, and the influence of inter-species signaling on C. albicans colonization and biofilm formation. These factors are key components in C. albicans ability to cause oral and vaginal thrush, denture stomatitis, and systemic infection, especially in immune compromised individuals.