The Dahms group currently studies microbial responses to external stimuli, including mechanisms associated with carbohydrate remodeling. We pioneered techniques to study the surface ultrastructure and physical properties associated with polarized and non-polarized growth in whole, live cells of moss (Physcomitrella patens) and fungi (Aspergillus nidulans) by atomic force microscopy (AFM). More recently we have been exploring invasion mechanisms for pathogenic (Escherichia coli, Pantoea stewartii, Neisseria gonorrhoeae) and symbiotic (Rhizobium leguminosarum) bacteria, and opportunistic fungal/yeast pathogens (A. nidulans, Candida albicans and krusei). We use a battery of microscopy techniques including AFM, fluorescence, laser scanning confocal (two-photon), transmission and scanning electron microscopy, to complement biochemical approaches. Of special interest to the group is how the microbial cell surface responds directly to external stimuli (calcium, copper, 2,4-D herbicide, antifungal agents) and how it is remodeled during growth, differentiation, and biofilm formation in wild type and genetically engineered microbes.