The goal of Dr. Piepenbrink’s research program is to elucidate the molecular mechanisms by which bacteria interact with their surroundings; this includes host cells, abiotic surfaces, extracellular structures and, in particular, other bacteria. Our group is approaching these basic questions by applying the lenses of structural biology and biophysics to microbial surface structures. These studies further seek to explain the phenotypic differences between bacterial strains of similar genetic background; typically, by comparing pathogenic bacteria to their commensal or environmental counterparts. The current focus is on type IV filaments, a class of extracellular appendages common to a wide range of bacteria, both Gram-positive and Gram-negative. To these ends, we are i) determining the high-resolution three-dimensional structures of the proteins and glycoproteins which make up extracellular assemblies, ii) using lower-resolution structural techniques in combination with molecular modelling to understand how protein subunits are assembled into these extracellular superstructures, iii) identifying substrates for intermolecular interactions that underpin the adhesive activity of pili and other bacterial appendages and iv) elucidating the role of extracellular polymers, particularly protein fibers and polysaccharides, in promoting and stabilizing bacterial biofilms.