SEM observation of Fresh Water Microorganisms Prepared by the Water Freeze-drying Method - 1 (Cyanobacteria)

Abstract

　During morphological studies of microorganisms using SEM, chemical processing of samples often results in artificially modified microstructures. The water freeze-drying method is a unique process that can be used to prepare SEM samples without using artificial chemicals. The results of freshwater cyanobacteria sample preparation using this method were compared to those of samples fixed in advance using glutaraldehyde and samples where no fixation was performed. The internal structures of the fractured samples were also observed. The comparison between samples confirmed that, in many species, the surface shape and internal structures were well preserved without using chemical fixation, and that cell components, such as thylakoids in Oscillatoria and gas cells in Microcystis, could be observed in a shorter time than using conventional methods. We found that the mucilaginous sheath of Microcystis aeruginosa and Microcystis viridis were partitioned by bulkheads, and contained cells. The time required for specimen preparation using the water freeze-drying and fracturing method is approximately 1 hour. The method not only preserves fine structures well, it also has the advantage of simple and safe sample preparation compared to conventional methods.