Abstract
Bacteria exhibit chemotaxis accumulating in higher concentration places by reducing frequency of tumbles (changes of the swimming direction) when they approach an attractant. This process of the chemotaxis has been ever simulated by using the biased random walk model. In this study, we verify the simulation model by measuring the time variation of the distribution of Salmonella typhimurium cells around the tip of a capillary filled with an attractant (0.05 M serine). The steady distribution of cells is reached in 10 - 20 minutes, where the number density of cells decays exponentially with the distance from the attractant. In the biased random walk simulation, a model cell is assumed to move toward the same direction as the previous step with the probability of α and change moving direction randomly with the probability 1 - α when the cell approaches the attractant. When the model cell recedes from the attractant, it changes moving direction randomly. Velocity and directional change of the model cells were determined from the observed results for salmonella cells. The steady distribution with exponential decay is also obtained for the simulation. The profile of the steady distribution depends on the value of α.
