Diffusion in Pseudomonas aeruginosa biofilms: a pulsed field gradient NMR study

A Pseudomonas aeruginosa biofilm is studied with pulsed field gradient echo nuclear magnetic resonance. Although not all spectral components are assig ned yet, the experimental results show that a biofilm consists of component s with very different diffusion coefficients. The various biofilm component s that give motionally narrowed H-1 NMR signals, can be grouped into five c lasses with diffusion coefficients, ranging from 2 x 10(-9) to 1 x 10(-13) m(2) s(-1). Investigation of the diffusion behavior of water in the biofilm shows three fractions with different diffusion coefficients. Besides the h ighly mobile bulk water at least two other fractions with much lower diffus ion coefficients are detected. It is shown that one of the fractions with t he low diffusion coefficient probably arises from intracellular water. Also for another component of the biofilm, glycerol, three fractions with diffu sion coefficients that differ more than a factor ten are detected. Also a g roup of signals exists which result from practically immobile components. ( C) 2000 Elsevier Science B.V. All rights reserved.