Measuring motility of soil bacteria in a microfluidic porous media model

PIRES MONTEIRO M.; S. MONTAGNA; V.I. MARCONI; A.R. LODEIRO; M. L. CORDERO

Congreso; 105 Reunión AFA; 2020

Bradyrhizobium diazoefficiens is a soil bacterium that possesses two different flagellar systems, subpolar flagella and lateral flagella. This soil bacterium fixes atmospheric N2 in symbiosis with soybean, being used as biofertilizer [1]. However, its direct inoculation in the soil is not enough for agroeconomic purposes, still requiring nitrogen supplementation. We use microfabricated devices to mimick the soil intrincated structure to study in a laboratory the bacterial motility and investigate the role of each flag- ellar system. In addition, we also use numerical simulations to model this system. We use two different types of microenvironments in this work, a polydimethylsiloxane (PDMS)/glass chamber to study the free movement of bacteria, and a PDMS/glass microfluidic device based on Voronoi Tesselations to characterize bacteria behavior under confinement conditions. We worked with two strains of Bradyrhi- zobium diazoefficiens, USDA 110 (Wild Type), which has the two flagellar systems; and one mutant, USDA 100 lafA that has only the subpolar flagellum. We investigate the dynamics of movement in microfluidic chambers and in microfluidic devices with different degrees of confinement. We analyze the frequency of each trajectory type for both strains and we quantify some parameters such as the average speed in each surface and turning angles. In addition, we compare the diffusion process of both cells in a soil model microenvironment. Furthermore, we compare our experimental results with simulations and a good accuracy is found between them. We hope in a brief future, to understand the Bradyrhizobium diazoefficiens cells dynamics in a soil environment, contributing to improve the inoculation process and as a consequence the efficiency of biofertilization.[1] Quelas JI, Althabegoiti MJ, Jimenez-sanchez C, Melgarejo AA, Marconi VI, Mongiardini EJ, et al. Swim- ming performance of Bradyrhizobium diazoefficiens is an emergent property of its two flagellar systems. Sci Rep 2016:1?14. https://doi.org/10.1038/srep23841.