The influence of the lipopolysaccharide (LPS) chain length on bacterial adhesion was investigated by measuring the collision efficiencies of three Escherichia coli K12 strains, each having a different length LPS, to silica glass beads in column tests (macroscale tests). Nanoscale interactions between the bacteria and a silicon nitride tip were probed utilizing atomic force microscopy (AFM). Adhesion results based on column tests indicated that collision efficiencies of the three bacteria were not consistently correlated to LPS length. Under conditions of low ionic strength (1 mM NaCl), collision efficiencies increased with LPS length for the three strains of E. coli. However, if cells were fixed with glutaraldehyde (2.5%), the strain with the shortest LPS chain had the greatest adhesion, while the bacterium with the mid-length LPS had the least adhesion to glass beads. Collision efficiencies increased when the solution ionic strength was increased from 1 to 100 mM as expected, and in most cases glutaraldehyde treatment also increased adhesion. AFM force curves failed to distinguish the adhesion characteristics of these bacteria measured in column tests, as all AFM force curves on the bacteria were identical. Changes in adhesion were also not predictable by more conventional measurements of bacterial properties based on ζ potential or contact angle. These results suggest that the LPS molecule length is not the sole determinant of adhesion of the three E. coli strains in porous media and that AFM force curve analysis, zeta potential, or contact angle data cannot yet be used to fully predict adhesion of these three strains to glass beads.
This work presents an interactive simulation software package for delivering an environmental engineering design project. The primary goal of the effort is to supplement theory-based course content with a complex and relevant design project, and to do so without increasing student course loads or placing excessive time demands on instructors. An additional goal for research-based instructors is to provide an efficient mechanism for infusing current research findings and experimental techniques into the curriculum. The software that administers the design project is called Interactive Site Investigation Software (ISIS). This paper summarizes the rationale for the development of ISIS, outlines the instructor-generated input required by ISIS, and details current ISIS features. These features allow students to drill boreholes, collect core samples, construct wells, collect groundwater samples, submit samples for laboratory analysis, and execute hydraulic and transport experiments at a virtual hazardous waste site. Initial feedback on the usability and usefulness of ISIS was generally positive, and the automated data requisition and dispensation substantially reduced the project's administrative demands on the instructor. Common student complaints pertained to controlled access to the software in the face of deadline pressure, uncertain expectations regarding their work product, and the need for real-time advice.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.