title: Electric polarization properties of single bacteria measured with electrostatic force microscopy.
abstract: We quantified the electrical polarization properties of single bacterial cells using electrostatic force microscopy. We found that the effective dielectric constant, ε(r,eff), for the four bacterial types investigated (Salmonella typhimurium, Escherchia coli, Lactobacilus sakei, and Listeria innocua) is around 3-5 under dry air conditions. Under ambient humidity, it increases to ε(r,eff) ∼ 6-7 for the Gram-negative bacterial types (S. typhimurium and E. coli) and to ε(r,eff) ∼ 15-20 for the Gram-positive ones (L. sakei and L. innocua). We show that the measured effective dielectric constants can be consistently interpreted in terms of the electric polarization properties of the biochemical components of the bacterial cell compartments and of their hydration state. These results demonstrate the potential of electrical studies of single bacterial cells.
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC) , C/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Esteban-Ferrer
authors.forename: Martin A
authors.initials: MA
authors.lastname: Edwards
authors.forename: Laura
authors.initials: L
authors.lastname: Fumagalli
authors.forename: Antonio
authors.initials: A
authors.lastname: Juárez
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gomila
mesh_terms: D018407:Bacterial Physiological Phenomena; D008853:Microscopy / Q000379:methods*; D055672:Static Electricity
keywords: dielectric constant; electric polarization; electrostatic force microscopy; gram-type; single bacteria