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ELECTRON MICROSCOPE STUDY OF THE RELATIONSHIP BETWEEN MESOSOME LOSS AND THE STABLE L STATE (OR PROTOPLAST STATE) IN
Abstract:
Ryter, Antoinette (Institut Pasteur, Paris, France), and Otto E. Landman. An electron microscope study of the relationship between mesosome loss and the stable L-state (or protoplast state) in Bacillus subtilis. J. Bacteriol. 88:457-467. 1964.-In a prior publication, it was postulated that inability of protoplasts to restart cell-wall synthesis and cell division and the inability of stable mass-conversion L forms to return to the bacillary state were both equivalent and both due to the interruption of a membrane-associated reaction sequence. It was further postulated that this reaction sequence might reside in the mesosome. In the present publication, it is shown by means of electron microscopy of thin sections that protoplasts and L forms do not contain mesosomes. The sequence of events leading to loss of the mesosomes during protoplasting is as follows. Soon after lysozyme addition, the mesosomes are extruded from the cell interior into the space between cell wall and cytoplasmic membrane. Mesosome fragments in the form of small vesicles gather at the poles of the cells and are released, along with intact protoplasts, when the wall fragments. (Sudden shift of bacilli to hypertonic environment also causes extrusion and fragmentation of mesosomes, but this damage is later repaired.) In intact bacilli, mesosomes are in contact with both the peripheral membrane and nuclear material. Upon extrusion of the mesosomes, a direct attachment between nuclear material and cytoplasmic membrane is observed. Deoxyribonucleic acid (DNA)-membrane attachment may play a role in the control of DNA replication. Bacillus subtilis L-colonies consist of irregularly shaped bodies of varying sizes, bounded only by a membrane. Many of the smaller bodies do not contain nuclear material, and many of the large ones appear inviable. Division is accomplished by a disorganized-appearing constriction process. There are no septa.
Insights
Mesosomes are lost when Bacillus subtilis forms protoplasts or L-forms, disrupting cell division and DNA replication. This loss is linked to membrane-associated reactions crucial for bacterial viability.
Area of Science:
- Microbiology
- Cell Biology
- Bacterial Genetics
Background:
- Previous research suggested a link between mesosomes and bacterial cell wall synthesis, division, and L-form stability.
- The mesosome was hypothesized to house a critical membrane-associated reaction sequence.
Purpose of the Study:
- To investigate the relationship between mesosome loss and the stable L-state (protoplast state) in Bacillus subtilis using electron microscopy.
- To elucidate the sequence of events leading to mesosome loss during protoplasting.
Main Methods:
- Electron microscopy of thin sections of Bacillus subtilis.
- Induction of protoplasts and L-forms using lysozyme and hypertonic environments.
Main Results:
- Protoplasts and L-forms of Bacillus subtilis lack mesosomes.
- Mesosomes are extruded from the cell interior during protoplasting and released when the cell wall fragments.
- Loss of mesosomes results in direct attachment between nuclear material and the cytoplasmic membrane, potentially affecting DNA replication.
- Bacillus subtilis L-colonies exhibit irregular shapes, variable sizes, and disorganized division without septa.
Conclusions:
- Mesosome loss is a key event in the formation of Bacillus subtilis protoplasts and L-forms.
- The absence of mesosomes may disrupt essential cellular processes like DNA replication and cell division.
- Understanding mesosome function is critical for comprehending bacterial viability and morphological changes.
