Project Summary/Abstract Studies of microorganisms have largely been carried out in free-floating (planktonic) cultures; however, the environmental and medical impacts of most microorganisms depend on their abilities to form resilient surface- associated microbial communities called biofilms. Biofilms are the predominant growth state of most microorganisms on biotic and abiotic surfaces. The overarching goal of my lab’s research program is to understand the molecular and mechanistic bases of microbial communities. We are interested in investigating how transcriptional networks underlie the regulation of gene expression during the development of microbial communities. Our overarching goals are to understand how these communities are regulated, how they are built, how their specialized properties are elaborated and maintained, and how these types of behaviors have evolved. We take systems biology approaches to address these biological questions and explore microbial communities at both the single-species as well as multi- species levels. The types of microorganisms we study include fungi, bacteria, and archaea, and vary from those that are found in the environment to commensals and opportunistic pathogens existing in the microbiota of mammalian hosts. Our central hypothesis is that there should be overlap in the molecular mechanisms used by microorganisms (even across kingdoms) to form microbial communities. This information will provide new insights into ways of treating biofilms in industrial and medical settings and, perhaps most importantly, in preventing them from forming in the first place. More broadly, this work may also shed light on the evolution of multicellularity in more recently evolved organisms.