Using Digital Holographic Microscopy to Characterize Vibrio's Chemotaxis

Vibrio alginolyticus is a marine bacterium that displays distinctive chemotactic behavior. Chemotaxis is the ability to move in response to a concentration gradient, either in the direction of nutrients or away from repellants. Vibrio's single, polar flagellum allows it to form a tight cloud in the presence of a chemoattractant. In this work, we experimentally characterize cloud sizes after both normal culture conditions and simulated microgravity using digital holographic microscopy or DHM. DHM allows visualization of volumetric samples by recording x,y,z and t information in holograms. Plane-by-plane reconstruction retrieves the z-plane information which can then by stitched together into hyperstacks for viewing. Although the resolution and cloud size prevent extensive single particle tracking, it still provides a comprehensive 3D picture of cloud formation and size in 3D. We discuss these observations and present possible future research avenues.