Heterologous Hosts and the Evolution and Study of Fungal Pathogenesis

Abstract

A variety of human bacterial and fungal pathogens are highly virulent in diverse nonvertebrate hosts. This chapter focuses on three invertebrate systems that have been used to study human fungal pathogens. It first discusses two genetically tractable hosts: the fly Drosophila melanogaster and the microscopic nematode Caenorhabditis elegans. Then it discusses the use of the greater wax moth caterpillar Galleria mellonella, which provides certain interesting technical advantages, even though it does not have a sequenced genome. The chapter briefly mentions other nonmammalian model hosts that have been used for the study of pathogenesis due to bacteria or parasites, which workers may wish to consider for the study of fungal pathogens. One of the exciting aspects of the C. elegans model is that it can be used to screen libraries of random mutants in order to identify hypovirulent mutants that can then be evaluated in mammalian models. The similarities between microbial pathogenesis in mammalian models and host-pathogen interactions in alternative model hosts suggest that certain virulence aspects of these pathogens may have developed during the interaction of these microbes with environmental predators. In addition to providing a paradigm for understanding the origin and maintenance of fungal virulence, these models provide invaluable insights into host-pathogen interactions in general.