Quantifying Biofilm Formation of <i>Sinorhizobium meliloti</i> Bacterial Strains in Microfluidic Platforms by Measuring the Diffusion Coefficient of Polystyrene Beads

Abstract

Though the majority of bacteria can form structured communities known as biofilms, mutations can cause bacterial strains to vary in their ability to form a biofilm. In this study, the apparent diffusion coefficient of polystyrene microspheres 0.29 µm in diameter, which were executing Brownian motion inside bacterial colonies, was used as a quantitative parameter of the ability of a strain to form a biofilm and of the biofilm development. The study was performed using five Sinorhizobium meliloti strains, the biofilm-forming strains Rm8530 expR + , Rm8530 exoY, and Rm9034 expG, and the non-biofilm forming strains Rm1021 and Rm9030-2 expA1. The green fluorescent beads were placed with each strain in a separate channel of a microfluidic device. Thus, as the bacterial colonies grew under identical conditions over a 4-day period, the motion of the fluorescent microspheres was recorded and the diffusion coefficients were measured every 24 hours via particle tracking algorithms. It was found that each strain displayed a unique pattern of change in diffusion coefficient over time. Also, for a given biofilm-forming strain, there was a clear correlation between the value of the diffusion coefficient and the appearance and motility of the bacterial community. Thus, the diffusion coefficient can be used to identify different S. meliloti strains, and for the biofilm-forming strains, it is also a quantitative indicator of the stage of biofilm development.

Microfluidic bioanalytical flow cells for biofilm studies: a review

“…It was first applied to biofilms 10 years ago with various follow-up studies since then, 169,170 including a recent on-chip study that should stimulate further work. 171,172 In that study, a parallel channel microfluidic device collected particle diffusion coefficient measurements and identification of 5 different Sinorhizobium meliloti bacterial strains during the first 4 days of growth. Nanoparticle tracking analysis (NTA) is a relatively new technique that monitors the motion of nanoparticles via the light scattered by the particles in dark-field mode.…”

“…It was first applied to biofilms 10 years ago with various follow-up studies since then, 169,170 including a recent on-chip study that should stimulate further work. 171,172 In that study, a parallel channel microfluidic device collected particle diffusion coefficient (i)…”