Microfluidic devices to simulate porous soil: modeling Bradyrhizorbium diazoefficiens motility

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

Antofagasta

Simposio; XXI Simposio Chileno de Física; 2018

IntroductionSeveral works are being developed to describe motility of bacteria propelled by flagella. In liquid medium the run-tumble model is wellestabilished to Escherichia coli and Salmonella [1].Our system of interested is a soil bacterium, Bradyrhizorbium diazoefficiens, that possesses two different flagellar systems,subpolar flagella and lateral flagella [2]. This bacterium fixes atmospheric N 2 in simbiosis with soybean, being used as biofertilizer. However its direct inoculation in the soil is not enough for agroeconomic purposes, still requiring nitrogen supplementation.We use microfluidic devices to simulate obstacles similar to the pores present in the soil to study the bacterial motility.Development The microfluidic device was fabricated via conventional photolithography process using polydimethylsiloxane (PDMS) polymer on a cover glass. We used different designs to simulate soil?s porous, one with square networks of widths 10 and 20 um, height 25um. Other based on Voronoi Tesselation [3] with three different widths 5, 10 and 20 um, all of them with 25 um of height. We worked with four strains of Bradyrhizorbium diazoefficiens, USDA 110 (Wild Type), which has two flagellar systems; and three mutants, USDA 110 ΔfliC that possesses only the lateral system, USDA 100 ΔlafA that has only the subpolar, USDA 110 ΔΔ which don?t express either flagellar system.We investigated bacterial motility of these Bradyrhizorbium diazoefficiens strains and tracked their trajectories with ImageJ software to understanding the process of competition for soybean nodulation. Figure 1 shows a 10μm width microchannel, inside red circles USDA 110 ΔFliC.