Difference in the chemotaxis between monotrichous and peritrichous bacteria clarified by a numerical simulation and observation

Abstract

We investigate difference in the chemotactic behavior between peritrichous bacteria (Salmonella typhimurium SJW1103) and monotrichous bacteria (Vibrio alginolyticus YM4). Bacterial chemotaxis occurs by suppressing the directional change and continue the straight swimming (run) when approaching the favorable region. The manner of the directional change differs between peritrichous and monotrichous bacteria, which may cause the difference in chemotaxis. The turn angle of a peritrichous bacterium tends to be random that change the posture by loosening the flagellar bundle, whereas a monotrichous bacterium with a single flagellum tend to turn behind by the rotational change of the flagellum. In the microscopic observation, chemotactic behavior of the cells is measured in the concentration gradient of the chemoattractant (L-serine) formed by diffusion from the tip of the glass capillary. V. alginolyticus cells accumulate around the attractant more rapidly and more densely than S. typhimurium. The numerical simulation where the observed run length and turn angle distribution were taken into account, well reproduces the observed result of the cells’ distribution. The reason for the higher number density in the monotrichous bacteria is the backward directional changes when receding from the attractant source. The degree of prolongation of average duration of runs toward the attractant source does not differ significantly between V. alginolyticus and S. typhimurium cells. Considering the probability with which the swimming direction changes in terms of approaching or receding from the attractant, we are able to relate quantitatively between the degree of accumulation and the turn angle distribution.

Keywords

• bacterial chemotaxis
• flagellum
• random walk
• attractant
• run
• reverse
• flick
• tumble