Scanning Electron Microscopy Techniques For Preservation and Observation Of Microbe-Mineral Assemblages and Biominerals

Scanning Electron Microscopy (SEM) of microbe-mineral assemblages can be challenging, especially when the objective is to characterize biominerals associated with cellular surfaces and exopolysaccharides (EPS). Biominerals are often loosely associated with the organic substrate on which they form making it difficult to determine the origin of minerals as biogenic or abiotic oxidation products. There are a variety of techniques that can be used for preservation of specimens ensuring that observation of desired relationships can be preserved. Here we examine various fixation, dehydration, and staining techniques using a suite of specimens in an effort to determine which technique works best with a particular type of biofilm. Types of biofilms used for this study included, biofilms attached to glass slides, flocculent non-cohesive biofilms, and cohesive highly mineralized biofilms. Microscopy was done to characterize the integrity of microorganisms, biominerals, microbemineral assemblages, alteration of specimens, and artifacts introduced during fixation and dehydration.