High-resolution visualization of Pseudomonas aeruginosa PAO1 biofilms by freeze-substitution transmission electron microscopy

Abstract

High-pressure freeze-substitution and transmission electron microscopy have been used for high-resolution imaging of the natural structure of a gram-negative biofilm.Unlike more conventional embedding techniques, this method confirms many of the observations seen by confocal microscopy but with finer structural detail.It further reveals that there is a structural complexity to biofilms at both the cellular and extracellular matrix levels that has not been seen before.Different domains of healthy and lysed cells exist randomly dispersed within a single biofilm as well as different structural organizations of exopolymers.Particulate matter is suspended within this network of fibers and appears to be an integral part of the exopolymeric substance (EPS).O-side chains extending from the outer membrane are integrated into EPS polymers so as to form a continuum.Together, the results support the concept of physical microenvironments within biofilms and show a complexity that was hitherto unknown.

Part of CIRS Nexus · Curated by Lauren Lowenstein, The Biotoxin Lady