Tracking the Movement of a Single Prokaryotic Cell in Extreme Environmental Conditions

Many bacterial species move toward favorable habitats. The flagellum is one of the most important machines required for the motility in solution and is conserved across a wide range of bacteria. The motility machinery is thought to function efficiently with a similar mechanism in a variety of environmental conditions, as many cells with similar machineries have been isolated from harsh environments. To understand the common mechanism and its diversity, microscopic examination of bacterial movements is a crucial step. Here, we describe a method to characterize the swimming motility of cells in extreme environmental conditions. This microscopy system enables acquisition of high-resolution images under high-pressure conditions. The temperature and oxygen concentration can also be manipulated. In addition, we also describe a method to track the movement of swimming cells using an ImageJ plugin. This enables characterization of the swimming motility of the selected cells.