Fig 1.
Left: The system consists of a food source that emits food particles (green), surrounded by BPs (black) and ABPs (red). Right: If an ABP runs into a food particle, it temporarily turns active and exhibits a persistent motion. The BP consumes food, too, but remains a passive Brownian walker. Which strategy is superior?
Table 1.
Simulation parameters and derived quantities.
Fig 2.
Particle densities in a stationary system.
Particle concentration as a function of (relative) distance to the center, for different sizes R of the reactor. Different colors stand for different radii of the containers (black: 200nm; red: 300nm; green: 400nm). Close to the food source, ABPs are active most of the time, leading to a significant depletion of their concentration. Close to the outer wall (right edge of the graphic), particle concentrations drop due to steric repulsion. Food-production rate: 50/μs; number of particles: 100 (of each species, ABPs and BPs); simulation time: 2s; boost time of ABPs: .
Fig 3.
Food consumption rates of particles for different sizes of the reactor. As a result of the bias of their density distributions, ABPs consume less food that BPs, exhibiting anti-chemotaxis. With increasing size of the reactor, the ratio of activated to inactive APBs is diminishing and their food consumption rates are approaching those of the BPs.
Fig 4.
Transient density distributions.
Time evolution of the density distributions of BPs (black) and ABPs (red), as well as food-particles (green, scaled down), for different time intervals. Initially, BPs and ABPs start at the distance rini = 200nm to the center, boundaries are absent. A burst of food particles occurs at the center at t = 0. Upon food consumption, the density distribution of ABPs advances rapidly toward the food source. Boost time of an ABP after consumption of a food-particle: .
Fig 5.
Food consumption in non-stationary setups.
Consumed food particles as a function of time after begin of the food burst. As a result of the bias of their density distributions, ABPs consume more food than BPs, exhibiting chemotaxis. The differences diminish with increasing initial distance rini to the center, since fewer ABPs are activated.
Fig 6.
Transient density distributions.
Time evolution of the density distributions of BPs (black) and ABPs (red), as well as food-particles (green, scaled down), averaged over the time interval of 0.1 < t < 0.15ms. Initial distance of the particles to the food source: rini = 200nm. Left panel: initial food profile was Gaussian, right panel: Initial food profile was a step-function. We remind that, despite the food being immobile, their profiles are depleted by the particles.
Fig 7.
Non-stationary food consumption.
Consumed food under the condition that the food concentration profile is a step function (green) or a Gaussian function (red). In the latter case, the ABPs experience an advantage over the passive BPs in terms of the amount of consumable food.