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Mesosomes in Escherichia coli
Abstract:
When Escherichia coli was grown in a synthetic medium and fixed with osmium, sections of the cells revealed clearly defined mesosomes. These mesosomes appeared to develop, in dividing cells, as coiled infoldings of the cytoplasmic membrane. Mature mesosomes formed a link between the cytoplasmic membrane and the nucleus of the cell. The arrangement of the mesosomes in dividing cells led to the hypothesis that division of the nucleus in these cells is accomplished by two separate polar mesosomes. One mesosome is derived from the parent cell and is present at one pole of the daughter cell. The other is freshly synthesized at or near the newly forming pole of the daughter cell. While the old mesosome remains attached to the chromosome received from the parent cell, the newly synthesized mesosome becomes attached to and initiates replication of the new chromosome. As the cell grows and elongates, the two mesosomes, attached to their respective chromosomes move apart, thus effecting nuclear division.
Insights
In Escherichia coli, mesosomes, which are cytoplasmic membrane infoldings, appear to play a crucial role in nuclear division. These structures may facilitate chromosome segregation during cell division.
Area of Science:
- Cell Biology
- Microbiology
- Molecular Biology
Background:
- Mesosomes are membrane structures observed in prokaryotic cells, particularly bacteria.
- Their precise function, especially during cell division, remains a subject of investigation.
Purpose of the Study:
- To investigate the role of mesosomes in the nuclear division of Escherichia coli.
- To elucidate the mechanism by which mesosomes contribute to chromosome segregation.
Main Methods:
- Culturing Escherichia coli in a synthetic medium.
- Cell fixation using osmium.
- Ultrastructural analysis of cell sections using electron microscopy.
Main Results:
- Clearly defined mesosomes were observed in fixed Escherichia coli cells.
- Mesosomes appeared as coiled infoldings of the cytoplasmic membrane during cell division.
- Mature mesosomes linked the cytoplasmic membrane to the cell nucleus.
Conclusions:
- A hypothesis is proposed where polar mesosomes facilitate nuclear division in Escherichia coli.
- One mesosome, inherited from the parent cell, attaches to the parent chromosome.
- A newly synthesized mesosome attaches to and initiates replication of the new chromosome, aiding segregation.