Bacteria are able to adhere to a wide variety of surfaces, both biotic and abiotic. For many bacterial pathogens, attachment to host tissues is a critical first step in the infection cycle. Our lab is interested in understanding how adhesion and mechanical forces control bacterial gene expression and virulence. One of the primary structures involved in E. coli adhesion is the type-1 fimbriae. These fimbriae are extended from the outer-membrane and specifically adhere to mannose sugars. For uropathogenic E. coli (UPEC), the ability to bind mannose allows these bacteria to adhere to mannosylated uroplakin proteins on bladder epithelial cells.
The biophysics of type-1 fimbriae is interesting in that it uses a catch-bond mechanism to regulate affinity. As tensile force is applied across the fimbriae, a conformational change occurs to increase substrate affinity. This mechanism allows UPEC to withstand the high fluid shear forces in the bladder.
To understand how fimbriae transduce mechanical cues to regulate bacterial behavior, our lab uses a multidisciplinary approach spanning traditional bacterial genetics, next-generation RNA expression profiling (RNAseq), and experimental biophysics (microfluidics and atomic force microscopy)
Bacterial cell shape regulation
Bacteria grow in a variety of cell shapes and often, these shapes can be dynamically regulated. In the case of Caulobacter crescentus, a long polar stalk is elongated in response to phosphate starvation. Despite decades of research, the composition of the stalk and the enzymes required for its synthesis remain unknown. Our lab is using genetic, microscopic, and mass spectrometry techniques to unravel the mechanisms of stalk elongation.
In collaboration with Drs. Danny Bubb and Sean O’Malley (Physics Department), we are studying the antimicrobial properties of metal nanoparticles. While these particles have well established toxicities towards E. coli, the exact mechanism of toxicity is not well understood. We have isolated a silver-nanoparticle resistant E. coli mutant and are in the process of identifying the causative mutation. We are also examining the role of particle size, composition, and environmental conditions on NP toxicity.