Interaction between Vibrio cholerae and Dictylostelium discoideum

描述(申请人提供)：弧菌种类主要是水生细菌。虽然它们中的许多是非致病性的，但一些弧菌与人类的严重疾病有关。尤其是霍乱弧菌，长期以来一直导致霍乱流行和大流行。霍乱的原因是霍乱弧菌在小肠的定植，在那里它产生一种强烈的毒素，导致大量水分损失和电解质失衡。在自然界中，霍乱弧菌可能是自由生活的，但它的生存似乎受到与其他生物的特定联系的青睐。霍乱弧菌形成这些联系并在其水生生态系统中生存所需的一些基因也参与了促进人类疾病的过程。体外研究表明，原生动物既可以利用霍乱弧菌作为食物来源，又可以促进霍乱弧菌的存活，但这些相互作用的性质尚不清楚。我们的研究重点将集中在霍乱弧菌和模式原生动物盘状阿米巴之间的关系，我们的实验室将这两种生物的专业知识结合在一起。我们的假设是霍乱弧菌在环境中受到阿米巴的捕食，霍乱毒素等毒力因子的产生有助于保护霍乱弧菌免受捕食，并提高其存活率。此外，我们认为盘状螺旋体可以作为霍乱弧菌与阿米巴相互作用的模型。我们将使用遗传学、生物化学和细胞生物学的方法来剖析盘状芽孢杆菌和霍乱弧菌之间的关系。突变分析和遗传筛选将被用来鉴定在盘状芽孢杆菌存在下生存和持续所需的霍乱弧菌基因，我们将利用细胞生物学技术开始阐明盘状芽孢杆菌和霍乱弧菌之间的相互作用。其具体目的是(I)鉴定参与抵抗阿米巴捕食的霍乱弧菌基因，(Ii)确定霍乱弧菌在盘状芽孢杆菌中的生存机制，以及(Iii)确定在阿米巴存在下生长的霍乱弧菌是传染性的还是超强毒力的。了解这种捕食者/被捕食者的关系不仅将提供有关环境中霍乱弧菌的基本信息，还可能为更好地控制霍乱弧菌的环境来源提供线索，从而有助于预防霍乱的流行。与公共卫生相关：霍乱弧菌是全世界发病率和死亡率的主要原因。这种细菌在自然界中有一个储存库，并定期重新出现，导致霍乱流行和大流行。为了在野外生存，霍乱弧菌必须能够抵抗阿米巴的捕食。为确定霍乱弧菌抵抗捕食的机制而进行的研究将有助于更好地了解霍乱弧菌的生态学。这可能会使制定控制霍乱疫情源头的战略成为可能。

DESCRIPTION (provided by applicant): Vibrio species are predominantly aquatic bacteria. While many of them are non-pathogenic, some vibrios are associated with severe disease in humans. Vibrio cholerae, in particular, has a long history of causing epidemic and pandemic cholera. Cholera results from colonization of the small intestine by V. cholerae, where it produces a potent toxin that results in massive water loss and electrolyte imbalance. In nature, V. cholerae may be found free-living, but its survival appears to be favored by specific associations with other organisms. Some of the genes required for V. cholerae to form these associations and persist in its aquatic ecosystem are also involved in promoting disease in humans. In vitro studies have suggested that protozoans may both use V. cholerae as a food source and promote V. cholerae survival, but the nature of these interactions is not well understood. Our studies will focus on the relationship between V. cholerae and the model protozoan amoeba Dictyostelium discoideum, and our laboratories have combined expertise in these two organisms. Our hypothesis is that V. cholerae is subject to predation by amoebae in the environment and that production of virulence factors such as cholera toxin helps protect V. cholerae from predation and enhances its survival. Further, we propose that D. discoideum can be used as a model for interaction of V. cholerae with amoebae. We will use genetic, biochemical, and cellular biology approaches to dissect the relationship between D. discoideum and V. cholerae. Analysis of mutants and genetic screens will be used to identify the V. cholerae genes required for survival and persistence in the presence of D. discoideum, and we will use cellular biology techniques to begin to elucidate the interactions between D. discoideum and V. cholerae. The specific aims are to (i) identify V. cholerae genes involved in resistance to predation by amoebae, (ii) determine the mechanism of survival of V. cholerae within D. discoideum, and (iii) determine whether V. cholerae grown in the presence of the amoeba are infectious or hypervirulent. Understanding this predator/prey relationship will not only provide basic information about V. cholerae in the environment, but also may provide clues to methods for better controlling the environmental sources of V. cholerae and thereby help prevent epidemics of cholera. PUBLIC HEALTH RELEVANCE: Vibrio cholerae is a major cause of morbidity and mortality worldwide. This bacterium has a reservoir in nature and periodically re-emerges to cause epidemics and pandemics of cholera. In order to persist in the wild, V. cholerae must be able to resist predation by amoebae. The proposed studies to determine the mechanisms of resistance to predation will lead to a better understanding of the ecology of V. cholerae. This may allow the development of strategies to control the source of epidemic V. cholerae.