Comparison of the relative concentration of motile and non-motile bacteria in small pores

The effect of small pores (similar in size to the stomata of plants) on the diffusion constants and relative concentrations of non-motile, randomly motile and chemotactic bacteria is considered. It is shown that although the Brownian diffusion constant of non-motile bacteria is a couple of orders of magnitude lower than the diffusion constant of motile bacteria, non-motile bacteria will still be present in both short (100 μm) and long (0·5 cm) pores in similar numbers to motile bacteria. It is postulated that this is due, at least in part, to the smaller amount of excluded volume for non-flagellated bacteria.