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Abstract:
Failure of the cell to properly regulate the number and intracellular
positioning of their flagella, has detrimental effects on the cells'
swimming ability. The flagellation pattern of numerous bacteria is
regulated by the NTPases FlhF and FlhG. In general, FlhG controls the
number of flagella produced, whereas FlhF coordinates the position of
the flagella. In the human pathogen Vibrio parahaemolyticus, its single
flagellum is positioned and formed at the old cell pole. Here, we
describe the spatiotemporal localization of FlhF and FlhG in V.
parahaemolyticus and their effect on swimming motility. Absence of
either FlhF or FlhG caused a significant defect in swimming ability,
resulting in absence of flagella in a Delta flhF mutant and an aberrant
flagellated phenotype in Delta flhG. Both proteins localized to the cell
pole in a cell cycle-dependent manner, but displayed different patterns
of localization throughout the cell cycle. FlhF transitioned from a uni-
to bi-polar localization, as observed in other polarly flagellated
bacteria. Localization of FlhG was strictly dependent on the cell
pole-determinant HubP, while polar localization of FlhF was HubP
independent. Furthermore, localization of FlhF and FlhG was
interdependent and required for each other's proper intracellular
localization and recruitment to the cell pole. In the absence of HubP or
FlhF, FlhG forms non-polar foci in the cytoplasm of the cell, suggesting
the possibility of a secondary localization site within the cell besides
its recruitment to the cell poles.
