A protoplast is the living contents of a biological cell bounded by its cell membrane after removal of the cell wall. Removing the cell wall need not immediately destroy the cell membrane; stability depends on the preparation and surroundings. Lysozyme acts on susceptible bacterial peptidoglycan, not on cellulose or chitin, so it is not a universal wall-removal enzyme.
The 1953 paper The isolation of protoplasts from Bacillus megaterium by controlled treatment with lysozyme by Claes Weibull (pp. 688–690, Figures 2–3) tested Bacillus megaterium strain KM. Apparatus included a Klett-Summerson colorimeter with a red filter and a Spencer no. 8 phase-contrast microscope. Lysozyme in phosphate buffer produced empty residual bodies; adding sucrose preserved granular spheres. Diluting their surroundings caused rapid osmotic lysis.
The same study compared untreated, boiled, lysozyme-exposed and sucrose-protected samples. Filled, stoppered tubes reduced damage from air exposure. After centrifugation, a Beckman DU spectrophotometer measured ultraviolet wave absorption of the separated liquid. Protected samples resembled untreated controls in releasing little ultraviolet-absorbing material; boiled and unprotected samples released much more. Later-growth cultures reduced spontaneous breakdown as a confounder.[ref]
The isolation of protoplasts from Bacillus megaterium by controlled treatment with lysozyme by Claes Weibull. pp. 688–689, Materials and Methods; pp. 692–694, release comparison and Figure 6
Together, the shape and release readouts support removal of mechanical protection while a permeability barrier persists. They do not establish unchanged selective permeability to every solute, long-term viability, or universal susceptibility.
An instructive extension of this experimental logic is a matched comparison: lysozyme present or absent, crossed with osmotic support present or absent. Keep starting material, buffer, observation interval and handling comparable; include a blank to distinguish optical effects of reagents from changes in the biological cells. Then dilute already formed protoplasts as a separate intervention. This separates access and wall removal from failure after removal. These are proposed controls for interpreting the mechanism, not additional reported results from the historical paper. A fall in optical signal alone cannot establish rupture: shape changes also alter scattering of light.
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A protoplast is a plant or bacterial cell that has had its cell wall removed, allowing the study of the cell membrane and its components in isolation. In plants, protoplasts are crucial for a variety of applications, including genetic engineering, cell fusion experiments, and studies of cellular processes. The removal of the cell wall can be done using enzymes, such as cellulase or pectinase, that break down the cell wall components.