BIOFILM CRYOPREPARATION FOR SCANNING ELECTRON-MICROSCOPY

The standard practice for dehydration of biofilms prior to scanning electron microscopy involves a graded ethanol or acetone series replacement of water followed by critical point drying. However, this preparative procedure represents a labor intensive task which may incur specimen distortion due to successive solution changes. This paper, therefore, outlines an alternative procedure based on quench-freezing of biofilms in super-cooled slush nitrogen at minus 208 degree C followed by freeze drying. For comparative purposes, representative photomicrographs of cryoprepared and critical point dried biofilm organisms have been included. The expediency and simplicity of this technique warrants a recommendation for its application with many types of water and wastewater biofilms.