title: Macro- and nanoscale observations of adhesive behavior for several E. coli strains (O157:H7 and environmental isolates) on mineral surfaces.
abstract: Subsurface biobarriers can be conceived to attenuate the migration of pathogens by adhesion to mineral surfaces. Candidate biobarrier materials of varied surface characteristics (dolomite, alpha-alumina, silica, pyrophyllite, and Pyrax (a composite form of pyrophyllite, mica, and silica)) were tested for Escherichia coli adhesive capacity in macroscale continuous-flow columns. Atomic force microscopy (AFM) was used to determine nanoscale interaction energies. Predicted attractive interaction energies correlated well with macroscale adhesive behavior for tested E. coli strains. AFM measurements confirmed ExDLVO model predictions of attachment in the primary minima for E. coli O157:H7 and two environmental isolates E. coli (UCFL339 and UCFL-348) with MOPS conditioned Pyrax. In macroscale column experiments, pyrophyllite and Pyrax demonstrated significantly higher bacterial retention, higher deposition coefficients and lower initial cell breakthrough values for E. coli O157:H7 than did alpha-alumina, silica, or dolomite (pyrophyllite, 0.93, 3.56 h(-1), 3.2% ODo; Pyrax, 0.95, 3.73 h(-1), 2.8% ODo; alpha-alumina, 0.74, 1.60 h(-1), 33% ODo; silica, 0.63, 0.43 h(-1), 73% ODo; and dolomite, 0.33, 0.17 h(-1), 89% ODo, respectively). Bacterial hydrophilicity impacted cell retention in Pyrax columns with the relatively hydrophobic E. coli isolate UCFL-339 (0.99, 6.13 h(-1), 0.4% ODo) retained better than the more hydrophilic E. coli isolate UCFL348 (0.94, 3.70 h(-1), 3.6% ODo). The strong adhesive behavior of Pyrax was attributed to the hydrophobic (deltaGiwi = -32.4 mJ/m2) pyrophyllite component of the mineral. Vicinal water appears poised between the bacterial and the mineral surface during initial attachment. Overall, observed behavior of the various E. coli strains and the selected mineral surfaces was consistent with surface analyses, conducted at both the macro- and nanoscale.
authors.affiliation: Environmental Engineering Program and Microbiology Program, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Morrow
authors.forename: R
authors.initials: R
authors.lastname: Stratton
authors.forename: H H
authors.initials: HH
authors.lastname: Yang
authors.forename: B F
authors.initials: BF
authors.lastname: Smets
authors.forename: D
authors.initials: D
authors.lastname: Grasso
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D001422:Bacterial Adhesion; D002119:Calcium Carbonate / Q000737:chemistry; D019453:Escherichia coli O157 / Q000302:isolation & purification / Q000502:physiology*; D005516:Food Microbiology; D057927:Hydrophobic and Hydrophilic Interactions; D008274:Magnesium / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods; D008903:Minerals / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D008903:Minerals; C049037:aluminosilicate; D012822:Silicon Dioxide; D002119:Calcium Carbonate; D008274:Magnesium; D000537:Aluminum Oxide; C028042:calcium magnesium carbonate; C011934:mica