Applied Math Seminar

Date: October 5, 2015

Time: 4:00PM - 5:00PM

Location: BLOC 220

Speaker: Dr. Mario Di Salvo, Mario E. Di Salvo - Universidad Nacional de Córdoba, Argentina

Title: Energetics and dynamics of the motion of self-propelled bacteria in aqueous media

Abstract: Marine bacteria often reach high swimming speeds, either to beat Brownian forces or to explore their surroundings in search of nutrients. Nutrients in the oceans are often present in the form of micropatches, point sources that are available within limited time and space. It is, therefore, very interesting to study how self-propelled organisms administer their energetic resources in order to optimize space exploration. To perform this task, we present a model to investigate the relation between bacterial dynamics and changes in the energy stored by a bacterium. Noting the existence of two very different time scales, we use a quasistatic approximation to obtain information about the speed of the bacterium and the variation on the available energy. We analyze the particular cases where the absorption is null for being the microorganism in a resource-depleted medium, and the possible enhancement in the motility of bacteria when the nutrient intake is a function of their speed. For the first case, it is possible to determine the volume of the region that a starving bacterium may visit until it stops its motion, which will depend on bacterial size. For the last case we conclude that a fast-moving microorganism can substantially increase its swimming speed by taking advantage of the advective uptake of nutrient molecules. We also discuss the dependence of the energy transfer rate to the bacterial motors, finding that the space exploration is optimized when this rate is a linear function on the speed of the microorganism.