Isolation of Herpetosiphon giganteus and Ultrastructure Analysis by Electron Microscopy

Herpetosiphon giganteus is a filamentous gliding bacterium. Gliding motility is the movement of the cells over surfaces without the aid of flagella. The mechanism responsible for bacterial gliding motility has not been known and there are only a few data on Herpetosiphon giganteus. The aim of this study was to observe the ultrastructure and negative staining of isolated strains of Herpetosiphon giganteus to find any organelles of locomotion. First, 35 strains of gliding bacteria were isolated from soil, freshwater, mud and activated sewage sludge. Then, 8 strains very closely related to Herpetosiphon giganteus were used for further examination. For extracellular slime and fibril observation, photoelectron micrographs were taken from different patterns on the cell surface of strains that were negatively stained. Thin sections with and without lysozyme treatment were prepared and examined by transmission electron microscopy. When the filaments were negatively stained, fibrils were detected in young cultures. There were two different kinds of fibrils in this study. The extracellular slime of these organisms was clearly visible. Examination with the electron microscopy revealed neither flagella nor an axial filament of any kind. There was no evidence for external organelles of locomotion. The results indicated that ring like structure localized at the cell surface connected with fibrils is responsible for gliding movement. The secretion of slime is necessary for adhesion of the cell to a solid surface and for ease of movement.