Utilizing Atomic Force Microscopy To Explore The Biophysical Chemistry Of The Bacterial Predator Bdellovibrio Bacteriovorus

Biofilms are complex communities of bacteria that live at interfaces. They excrete a complex mix of polysaccharides, proteins, and nucleic acids, collectively called exopolymeric substances or EPS, that allow them to effectively stick onto various surfaces. Biofilms are difficult to remove using antibiotics, chemicals, and desiccation and thus Bdellovibrio bacteriovorus has been studied as a natural means of eradication. Bdellovibrio bacteriovorus is a predatory, gram-negative bacterium that preys upon other gram-negative bacteria. Bdellovibrios are able to effectively distinguish between eukaryotic cells, other bdellovibrios, and their prey, but the molecular mechanisms by which Bdellovibrio cells are able to selectively target their prey are unknown. In this study, the Atomic Force Microscope (AFM) is used to explore the biochemical and biophysical nature of the interactions between Bdellovibrio and their prey. We adhere Bdellovibrio cells tipless AFM cantilevers using an adhesive protein derived from the aquatic Blue Mussel. These Bdellovibrio cells are then used to directly probe specifically-modified surfaces by extending the tip until the cells gently contact the surface and then retracting it. NanoNewton-scale adhesion forces and nanometer-to-micron adhesive interaction lengths are measured quantitatively. These two nanoscale measurements obtained using Atomic Force Microscopy allow us to analyze differences in the molecular recognition of specific chemical groups by Bdellovibrio cells. Sample surfaces include silicon wafers chemically modified with charged, hydrophilic, and hydrophobic groups. These modified silicon surfaces serve to model the chemical properties of prey cells, which will help identify which specific molecules Bdellovibrio uses to recognize its prey.