Bacteria that can colonize multi-cellular organisms live in or on their hosts as part of complex communities. They use specific surface proteins to adhere to one another, and to host cells, to form a stable community of bacteria that are not washed away. In this research, mentored undergraduate students, will identify and characterize protein colonization factors and determine how they interact with one another. Hra1 was previously described as a member of the agglutinin family of outer surface proteins which by self-association mediates adjacent bacterial cells to adhere to one another. Hra1 also mediates in vivo binding of Escherichia coli to eukaryotic cells and specifically promotes colonization of nematode worm intestines in small aggregates. There is preliminary evidence that suggests that a second protein, Aap, prevents Hra1 mediated interactions. The inhibitory activity of Aap provides a mechanism for restricting Hra1 mediated associations as bacteria travel towards their intestinal niche. Once bacteria reach a suitable niche however, Aap must be removed for colonization to ensue. This research, will determine the mechanism for Aap removal and thus how Hra1 and Aap work together to ensure that bacteria can bind and disperse in a manner that optimizes colonization of nematode intestines. The project will also identify new surface factors involved in intestinal colonization and determine how, if at all, they interact with known surface proteins. In addition to identifying proteins involved in binding among identical bacteria, the project will focus on uncovering surface proteins that allow different species of bacteria to interact with one another, as a first step to understanding community organization among the many types of bacteria living within a single multi-cellular organism.
Broader Impact Bacteria are the most abundant life-forms on earth and colonize a wide variety of living and non-living niches by mechanisms that are not very well understood. This project will improve current understanding of how communities of bacteria are established and persist within other organisms, as well as add to knowledge on the structure and function of bacterial surface proteins. The research required to address questions relevant to this project will largely be performed by undergraduate students working at Haverford College and overseen by a principal investigator, who teaches there. The project will provide early opportunities for such students with the hope of increasing their interest and retention in science. Four to eight students, including women and other groups underrepresented in the sciences will be engaged in laboratory research projects each year. Several dozen other students will be enriched by course modules and classroom examples in courses that are developed and taught by the principal investigator. This includes 20-40 students who will participate in inquiry-based laboratory research courses each year that will expose them to skills in microbiology, molecular biology and computational science.
