OPUS: Synthesizing Defensive Symbiosis from a Microbial Perspective

Indiana University, Bloomington IN

Investigators

Abstract

Essentially all plants and animals are colonized by a diverse array of symbiotic microorganisms. For example, 90% of the cells in the human body are bacteria. Some microorganisms may be pathogens that cause disease or death of their hosts while others, such as gut bacteria of animals, may be essential for their nutrition and survival. A growing body of literature suggests that a number of symbiotic microorganisms play a defensive role, protecting their hosts against natural enemies such as parasites, pathogens and herbivores. The goal of this project is to review and synthesize the results of past studies to gain new insights into the underlying mechanisms and ecological consequences of defensive symbiosis. Past research leading to this goal has focused on two distinct groups of defensive symbionts: toxic alkaloid-producing fungal symbionts of grasses that make host plants poisonous to grazing animals and bacterial symbionts of ticks that may exclude pathogens or reduce their transmission. These interactions can provide a strong advantage to hosts, leading to an increase in the prevalence of defensive symbiosis. The major product of this project will be a book on defensive symbiosis that synthesizes previous research in relation to broader areas of research in ecology, microbiology and plant and animal health, and that highlights important areas for future research. A second product will be an open-access database from a 13-year experiment manipulating defensive symbiosis in experimental grasslands. Defensive symbiosis has significant impacts on our economy, the environment and human health. For example, toxin-producing fungal symbionts of grasses are a serious problem for grazing livestock but provide effective biocontrol against pests in turfgrass systems. Likewise, many arthropods host bacterial symbionts that inhibit pathogen infection or transmission, including important human pathogens, such as the dengue fever virus. In humans, altering our normal microbiota can lead to a number of health problems including disease. In sum, key species in many ecosystems are characterized by defensive symbiosis. The resulting book will provide a widely accessible and comprehensive body of past results, improving our understanding of defensive symbiosis and informing future applications of these interactions. The database will provide research opportunities for students and other scientists.