title: Bacterial adhesion to glass and metal-oxide surfaces.
abstract: Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was significantly (P < 10(-25)) correlated with total adhesion free energy (U) between the bacteria and surface (A = 2162e(-1.8U)). Although the correlation was significant, agreement between the model and data was poor for the low energy surfaces (R2 = 0.68), indicating that better models or additional methods to characterize bacteria and surfaces are still needed to more accurately describe initial bacterial adhesion to inorganic surfaces.
authors.affiliation: Environmental Engineering Program, The Pennsylvania State University at Harrisburg, Middletown, PA 17057, USA. bx128@psu.edu
authors.forename: Baikun
authors.initials: B
authors.lastname: Li
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Logan
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000502:physiology; D001422:Bacterial Adhesion / Q000187:drug effects / Q000502:physiology*; D016956:Burkholderia cepacia / Q000187:drug effects / Q000502:physiology; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000502:physiology; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000502:physiology; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000502:physiology; D057927:Hydrophobic and Hydrophilic Interactions; D008670:Metals / Q000737:chemistry / Q000494:pharmacology*; D010087:Oxides / Q000737:chemistry / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000502:physiology; D012822:Silicon Dioxide / Q000494:pharmacology*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D020099:Coated Materials, Biocompatible; D008670:Metals; D010087:Oxides; D014867:Water; D012822:Silicon Dioxide