`MO: Exploring the Symbiotic Association Between Tropical Social Insects and Actinomycetes

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Microbial pathogens cause virulent diseases in plants and animals, and thus are important agents of natural selection. Organisms use various methods to defend themselves from pathogens, including morphological structures (e.g., plant cell walls, exoskeleton in insects), physiological processes (e.g., immune systems), and behavior. Recent research on fungus-growing ants identified a previously poorly recognized approach to host defense: the symbiotic association of a host with antibiotic-producing bacteria in the order Actinomycetales. Actinomycetes are Gram-positive, filamentous bacteria that are well known for their ability to produce potent antibiotics. Indeed, the majority of known antibiotics used pharmaceutically are derived from actinomycetes. Theory predicts social insects to be especially vulnerable to parasites, given that their colonies harbor a high density of genetically homogenous individuals (increasing transmission rates) living in warm, moist conditions. This microbial observatory project explores the hypothesis that social insects frequently engage in symbiotic associations with antibiotic-producing actinomycetes to help defend against microbial pathogens. This hypothesis will be examined by combining intensive field sampling of social insects from two tropical geographic locations: Puerto Rico and Costa Rica. The three specific goals of this project are to: i) describe the broad microbial community associated with tropical social insects using biolipid markers, ii) detect actinomycetes within these microbial communities through a combination of culture-dependent and culture-independent methods, and iii) document the functional role of actinomycetes in host defense through experimental work with live insect colonies and symbiotic microorganisms. This study will provide greater understanding of the distribution and diversity of actinomycetes in nature as well as describe the broad microbial community composition associated with a diverse collection of tropical social insects. The results obtained will provide insights about the origin and maintenance of symbiotic associations between social insects and antibiotic-producing actinomycetes, as well as reveal how common this type of host defense mechanism is in nature. In addition, this project will have immediate and long lasting impacts in training, education, and infrastructure in the fields of tropical microbial ecology and symbiosis. With co-funding support from the NSF Office of International Science and Engineering, microbiology and ecology will be integrated on an international scale, including 3 different universities (U. of Wisconsin, U. of Puerto Rico and U. of Costa Rica) and worldwide by posting our findings on the internet. Thousands of K-12 students will be exposed each year to exhibits on symbiotic associations between microbes and social insects, both in Madison, WI and in Costa Rica. Broader impacts in Costa Rica include the training of local parataxonomists, following the outreach program created by Dr. Daniel Janzen, and additional contributions towards improvements of microbiology facilities within the Área de Conservación Guanacaste (ACG). This MO will also impact underrepresented students directly by providing undergraduate and graduate level research experiences at U. of Puerto Rico. Finally, this research could lead to the development of new sources for discovering novel antibiotics that may have applications in agriculture and medicine.