Measuring motility of soil bacteria in a microfluidic porous media model

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

Cordoba

Congreso; II Brazil-Argentine Microfluidics Congress; 2019

Bradyrhizobium diazoefficiens is a soil bacterium that possesses two different flagellar sys- tems, 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 intricate structure to study in a labo- ratory the bacterial motility and investigate the role of each flagellar 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 tessellations[2] to characterize bacteria behavior under confinement conditions. We worked with four strains of Bradyrhizobium diazoefficiens, USDA 110 (Wild Type), which has the two flagellar systems; and three mutants, USDA 110 fliC that possesses only the lateral system, USDA 100 lafA that has only the subpolar flagellum, and USDA 110 which do not express any flagellar system. We count the number of Bradyrhizorbium diazoeffi- ciens cells and we obtain a relation between cells accumulation and type of surface, glass and PDMS, as well as in bulk, using the microfabricated chambers. We choose two strains, USDA 110 and USDA 110 lafA, to investigate the dynamics of movement in microflu- idic devices with different degrees of confinement. We analyze the frequency of different trajectory types 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 environ- ment, 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. Swimming performance of Bradyrhizobium diazoefficiens is an emergent property of its two flagellar systems. Sci Rep 2016:1?14. doi:10.1038/srep23841.[2] Wu M, Xiao F, Johnson-Paben RM, Retterer ST, Yin X, Neeves KB. Single- and two-phase flow in microfluidic porous media analogs based on Voronoi tessellation. Lab Chip 2012;12:253?61. doi:10.1039/c1lc20838a.