OPEN ACCESS
doi:
- Nanxi Lu *a,
- Arash Massoudiehb,
- Xiaomeng Liangb,
- Dehong Huc,
- Tamir Kamaid,
- Timothy R. Ginnf,
- Julie L. Zillesa and
- Thanh H. Nguyena
- a Dep. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
b Civil Engineering Dep., The Catholic Univ. of America, 620 Michigan Ave. NE, Washington, DC 20064, USA
c Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, WA 99352, USA
d Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Bet Dagan, Israel
f Dep. of Civil and Environmental Engineering, Univ. of California, Davis, Davis, CA, USA
- Statistical cluster analyses of cell trajectories separated actively swimming cells from nonswimming ones.
- Motility was evaluated in multiple porous media model systems with increasing complexity.
- Strong motility changed trajectories near the surface and reduced attachment.
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 Azotobacter vinelandii 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 nifH− 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.
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