C.A. (Cyrus) Mallon, PhD

Project Title: Insights into Microbial Invasions: The Effect of Microbial Diversity on the Survival Escherichia coli

Description: Any species that is introduced into a foreign range—with or without intent, anthropogenically or naturally—and manages to survive for an extended period of time can be considered an invasive species. There is a plethora of work done on invasive species, however nearly all of these studies focus on the patterns of invasion rather than their mechanisms. The mechanisms of invasion are important to understand because invasions are bigger threats to local biodiversity and ecosystem functioning than any other perturbation or disturbance. As humans, we rely on crucial ecosystem services for survival, like clean water for drinking, healthy forests for timber harvest, and even rare plants for medicinal use. Thus, it is important to study the causes and effects of invasions so that we may preserve our current ecosystems and restore those that have collapsed.

                The primary focus of my research is to unlock the mechanisms of microbial invasions. By using a non-pathogenic derivative of the pathogen Escherichia coli 0157:H7 as a model organism, my research aims to understand how the components of diversity—species richness, composition, evenness, and functional diversity—affect the fate of E. coli 0157:H7 in soil environments. Two mechanisms that may influence the invader’s survival in soil are the complementarity and selection effect. For instance, communities with higher diversity may limit an invader’s access to resources (complementarity for resource use in the native flora); or, one or a few highly competitive species could outcompete the invader for niche space (selection of dominant organism(s) in the native community). It has been shown by Salles etal (2009) that highly diverse communities can use more nutrient resources from the soil and function at higher process rates (e.g., denitrification or CO2 production) than less diverse communities. Furthermore, a direct link between the diversity of the resident microbial community and the invader’s survival was observed in van Elsas etal (2012), and preliminary evidence indicated competition for resources is a major factor determining the invader’s fate.