Swimming Motility ReducesAzotobacter vinelandiiDeposition to Silica Surfaces

Abstract

The transport and fate of bacteria in porous media is influenced by physicochemical and biological properties. This study investigated the effect of swimming motility on the attachment of cells to silica surfaces through comprehensive analysis of cell deposition in model porous media. Distinct motilities were quantified for different strains using global and cluster-based statistical analyses of microscopic images taken under no-flow condition. The wild-type, flagellated strain DJ showed strong swimming as a result of the actively swimming subpopulation whose average speed was 25.6 μm/s; the impaired swimming of strain DJ77 was attributed to the lower average speed of 17.4 μm/s in its actively swimming subpopulation; and both the nonflagellated JZ52 and chemically treated DJ cells were nonmotile. The approach and deposition of these bacterial cells were analyzed in porous media setups, including single-collector radial stagnation point flow cells (RSPF) and two-dimensional multiple-collector micromodels under well-defined hydrodynamic conditions. In RSPF experiments, both swimming and nonmotile cells moved with the flow when at a distance ≥20 μm above the collector surface. Closer to the surface, DJ cells showed both horizontal and vertical movement, limiting their contact with the surface, while chemically treated DJ cells moved with the flow to reach the surface. These results explain how wild-type swimming reduces attachment. In agreement, the deposition in micromodels was also lowest for DJ compared with those for DJ77 and JZ52. Wild-type swimming specifically reduced deposition on the upstream surfaces of the micromodel collectors. Conducted under environmentally relevant hydrodynamic conditions, the results suggest that swimming motility is an important characteristic for bacterial deposition and transport in the environment.

Confined Flow: Consequences and Implications for Bacteria and Biofilms

“…Because surface attachment also involves short-range interactions, however, different strains of bacteria may exhibit other behaviors. As one example, swimming motility of the soil bacterium Azotobacter vinelandii reduces attachment in model 2D glass micropillar arrays (106). Thus, specific physicochemical interactions may still alter attachment processes even when the dominant transport process is the same.…”

Current examining methods and mathematical models of horizontal transfer of antibiotic resistance genes in the environment

“…Transformation models are gradually developed referring to the establishment process of conjugation models. Lu et al adapted from the mass action law, allowing the transformation frequency by the proposed model to be influenced by varied DNA or cell concentrations Frontiers in Microbiology 07 frontiersin.org (Lu et al, 2015). This was the first transformation dynamics model, successfully predicting the natural transformation frequencies of tetracycline resistance genes in both motile and non-motile strains of Azotobacter vinelandii.…”

Microbial Transport and Fate in the Subsurface Environment: Introduction to the Special Section

“…In cleverly designed laboratory experiments, Lu et al (2015) investigate the effect of swimming motility on the attachment of bacteria to porous media. Different strains of Azotobacter vinelandii cells and silica surfaces served as model systems for a comprehensive analysis of cell trajectories and deposition in a radial stagnation point flow cell and in a two‐dimensional multiple‐collector micromodel.…”