Noticimat: 04

Título: Modeling chemically-mediated antagonistic interactions between bacterial cells at two different scales
Ponente: Dr. Eneas Aguirre von Wobeser (Instituto Nacional de Ecología)
Lugar: G101 salón "Diego Bricio Hernández"
Hora: 1:00 pm
Resumen: The microbial world is rich in complex interactions between cells, populations, and even communities and ecosystems, which take place at scales ranging from molecular to planet-wide. Thus, determining appropriate scales for modeling those interactions is critical to obtain meaningful results. We were interested in modeling the production of antimicrobial substances by bacterial cells, which is a common type of interaction in almost any microbial community, in which a strain gains competitive advantage by inhibiting or killing other cells. Specifically, we give estimates of the order of magnitude of the costs of those interactions, in terms of resources invested in producing the molecules involved. Even though we are dealing with a single interaction mechanism, chemically-mediated antagonistic interactions, large variations in the numbers of molecules involved call for different mathematical treatment at different scales. At the very small scale, we considered the random diffusion of single molecules away from the producing cell. For this scenario, the time a molecule stays close to a cell was simulated considering random steps, and could be adjusted to an Inverse Gaussian Distribution. Using this approach we could estimate that a cell would need to invest 3.92×10−22kgs−1 of organic matter, which is 9 orders of magnitude lower than the estimated expense for growth. On the other hand, for many cells it would be useful to maintain a certain concentration of antimicrobial compounds around itself. In this scenario, the large number of molecules prevented modeling their trajectories individually. Thus, we used differential equations and modeled them as continuous concentrations. These results indicated that, in this scenario, cells would need to invest 1.20×10−11kgs−1, which is 2 orders of magnitude higher than the cost of growth. Since this figure is not likely to be sustainable, the real expense is probably intermediate between these two extremes.