CHARACTERIZATION OF THE DIFFUSIVE PROPERTIES OF BIOFILMS USING PULSED-FIELD GRADIENT-NUCLEAR MAGNETIC-RESONANCE

The mobility of water in intact biofilms was measured with pulsed fiel d gradient nuclear magnetic resonance (PFG-NMR) and used to characteri se their diffusive properties. The results obtained with several well- defined systems, viz. pure water, agar, and agar containing inert part icles or active bacteria were compared to glucose diffusion coefficien ts measured with microelectrodes and those calculated utilising theore tical diffusion models. A good correspondence was observed indicating that PFG-NMR should also enable the measurement of diffusion coefficie nts in heterogeneous biological systems. Diffusion coefficients of sev eral types of natural biofilms were measured as well and these results were related to the physical biofilm characteristics. The values had a high accuracy and reflected the properties of a sample of ca. 100 bi ofilms, while nonuniformity or non-geometrical shapes did not negative ly influence the results. The monitored PFG-NMR signal contains supple mentary information on e.g. cell fraction or spatial organisation but quantitative analysis was not yet possible. (C) 1998 John Wiley & Sons , Inc.