Abstract
Bacteria such as Escherichia coli and Salmonella enterica swim in liquid media using the bacterial flagella. The flagellum consists of the basal body (rotary motor), the hook (universal joint) and the filament (helical screw). Since mutants with a defect in flagellar assembly and function cannot swim smoothly, motility assay is an easy way to characterize flagellar mutants. Here, we describe how to measure free-swimming speeds of Salmonella motile cells in liquid media. Free-swimming behavior under a microscope shows a significant variation among bacterial cells.
Keywords: Bacterial flagella, Motility, Motor, Optical microscopy, Proton motive force, Salmonella
Background
The flagellar motor of E. coli and Salmonella is powered by downhill proton translocation along proton motive force (PMF) across the cytoplasmic membrane (Morimoto and Minamino, 2014; Minamino and Imada, 2015). The rotational speed of the proton-driven flagellar motor is proportional to total PMF (Gabel and Berg, 2003). Therefore, measurements of free-swimming speeds of motile cells allow us not only to analyze motor performance of various mutants but also to examine whether there is a significant difference in total PMF under experimental conditions (Minamino et al., 2016).
Materials and Reagents
Equipment
Software
Procedure
Note: Carry out procedures at ca. 23 °C unless otherwise specified.
Data analysis
Notes
Recipes
Acknowledgments
This protocol was modified from a previous work (Minamino et al., 2003). This research has been supported in part by JSPS KAKENHI Grant Numbers JP15K14498 and JP15H05593 to YVM, JP21227006 and JP25000013 to KN and JP26293097 to TM and MEXT KAKENHI Grant Numbers JP26115720 and JP15H01335 to YVM and JP23115008, JP24117004, JP25121718 and JP15H01640 to TM.
References
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