Lysis of about 90% of the cells of Acetobacter xylinum by lysozyme may be obtained after 2 hours at pH 8.1 in phosphate–citrate buffer. The cell population is heterogeneous since the remaining 10% of the cells do not lyse, even on repetition of the above treatment. The lysozyme does not cause the dissolution of all the bacterial wall, as in other lysozyme-sensitive species, but appears to attack only a limited, local area on the surface of the bacterium. Following the local weakening of the wall, the cell contents escape into the medium leaving a distinct "hull" with the same size and shape as the cell. The oxidative capacity of the lysed cells is the same as that of the whole cells. Reasons for the heterogeneity of the bacterial wall, both within and between cells, remain obscure.