Electron microscopic observations on the excretion of cell-wall material by Vibrio cholerae

Abstract

Thin sections of Vibrio cholerae harvested during the logarithmic phase of growth in alkaline peptone water or in syncase medium have revealed an excretion process of the cell wall in the form of bulging out and pinching-off of portions. An identical phenomenon has also been revealed in cells harvested after a short period of incubation (1·5 hr) in glucose saline solution at 37°. Particles closely resembling the pinched-off cell-wall structures have been detected by metal shadowing and negative staining techniques in the bacteria-free filtrates of the log phase cultures (in both media) and the glucose saline incubation medium. These particles are in the range 400-1100 Å in size with a maximum frequency in the range 600-800 Å. No similar cell-wall changes have been detected in vibrios-harvested from the stationary phase of growth in any of the culture media, nor in vibrios undergoing plasmolysis. Turbidi-metric tests revealed no significant lysis of the vibrios when harvested during the logarithmic growth phase and incubated for several hours in saline or in Kellenberger buffer as compared to the lysis detected in distilled water. It is suggested that the cell-wall process described represents an excretory mechanism of V. cholerae, and the nature of the products released by the young vibrios and their probable relation with cholera toxin is discussed.