Cryoscanning electron microscopy of microbial extracellular polysaccharides and their association with minerals

Abstract

The morphology of pure microbial extracellular polysaccharides (EPS) and of their association with a mineral was studied by scanning electron microscopy. Several methods were compared: cryo‐SEM, critical point dehydration (CPD), and TEM observation after solvent exchanges and inclusion in a resin. The EPS were observed as fibrils, interconnected into a network. Their dimensions were compared with literature data on the conformation and shape of the given EPS. It was deduced that these EPS have an undoubtably fibrillar structure when hydrated, and that some aggregation or collapse artifacts took place in both CPD or cryo‐SEM samples but were quite limited. Cryo‐SEM appears then as a relevant tool for the study of the secretion of EPS by microorganisms in soils. Copyright © 1992 Foundation for Advances in Medicine and Science, Inc.