Spontaneous Protoplast Formation by Methanosarcina barkeri

Methanosarcina barkeri strain FR-19 lysed spontaneously in substrate-depleted cultures. The addition of 0.3 M-sucrose prevented complete lysis and resulted in the formation of osmotically sensitive UV-fluorescent spheres. Electron microscopic examination showed that complete degradation of the cell wall occurred before the release of true protoplasts, which were stabilized by sucrose and glucose (0.2-0.3 M) but not by glycerol. Exponentially increasing methane production and regeneration of protoplasts could not be demonstrated.