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.
Highlights
IntroductionBiofilms, such as dental plaque, the slime that forms on surfaces in areas with
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
D is the same for all strains on Day 0 and is the same as the value for the control, as was confirmed by statistical analysis. These results were expected, since the data taken on Day 0 represent the bacteria-bead solution when it was just inserted in the microfluidic channel
Summary
Biofilms, such as dental plaque, the slime that forms on surfaces in areas with. C. Cheng et al 158 water, and the biofilms found on catheter infections, are structured communities of bacteria. Biofilms are formed by the majority of bacteria in natural and pathogenic ecosystems. Unlike a simple aggregation of bacterial cells, the bacteria in a biofilm are surrounded by a mixture of polymers, known as the extracellular polymeric substance (EPS). In order to prevent the formation of harmful biofilms, it is essential to quantify bacterial growth and biofilm development as well as be able to distinguish between bacterial strains that can form biofilms from strains that cannot. Exactly because biofilm formation is contingent on the secretion of the polysaccharides that form the EPS matrix, rates of cell division alone are not enough to quantify biofilm development
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