title: A novel planar flow cell for studies of biofilm heterogeneity and flow-biofilm interactions.
abstract: Biofilms are microbial communities growing on surfaces, and are ubiquitous in nature, in bioreactors, and in human infection. Coupling between physical, chemical, and biological processes is known to regulate the development of biofilms; however, current experimental systems do not provide sufficient control of environmental conditions to enable detailed investigations of these complex interactions. We developed a novel planar flow cell that supports biofilm growth under complex two-dimensional fluid flow conditions. This device provides precise control of flow conditions and can be used to create well-defined physical and chemical gradients that significantly affect biofilm heterogeneity. Moreover, the top and bottom of the flow chamber are transparent, so biofilm growth and flow conditions are fully observable using non-invasive confocal microscopy and high-resolution video imaging. To demonstrate the capability of the device, we observed the growth of Pseudomonas aeruginosa biofilms under imposed flow gradients. We found a positive relationship between patterns of fluid velocity and biofilm biomass due to faster microbial growth under conditions of greater local nutrient influx, but this relationship eventually reversed because high hydrodynamic shear leads to the detachment of cells from the surface. These results reveal that flow gradients play a critical role in the development of biofilm communities. By providing new capability for observing biofilm growth, solute and particle transport, and net chemical transformations under user-specified environmental gradients, this new planar flow cell system has broad utility for studies of environmental biotechnology and basic biofilm microbiology, as well as applications in bioreactor design, environmental engineering, biogeochemistry, geomicrobiology, and biomedical research.
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University, A314 Technological Institute, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Tadas S
authors.initials: TS
authors.lastname: Sileika
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Jisun
authors.initials: J
authors.lastname: Lee
authors.forename: Aaron I
authors.initials: AI
authors.lastname: Packman
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D018441:Biofilms / Q000254:growth & development*; D005434:Flow Cytometry / Q000295:instrumentation*; D057446:Hydrodynamics; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000502:physiology*; D013314:Stress, Mechanical; D013312:Stress, Physiological