Studies on the deoxyribonucleic acid-bearing portion of the cell envelope of Escherichia coli
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Abstract:
The envelope components of nuclear bodies which were obtained from Escherichia coli W7 by a mild lysis method were investigated. By using 2,6-diaminopimelic acid (DAP) as precursor which is incorporated only into peptidoglycan in this strain it was found that the particles contained about 14% of the murein layer of the cell. The percentage of phosphatidylethanolamine was enriched at the cost of the other phospholipids in the nuclear bodies compared to whole cells. If lipids were labelled with 3H-palmitic acid the cytoplasmic and the outer membrane could be found after isopycnic centrifugation; however, when the cells were incubated with chloramphenicol, only the outer membrane was seen. The peptidoglycan and the proteins could be assigned only to the outer membrane. The DNA is also bound to the outer membrane. From these results it was concluded that (1) in all lysis methods the cytoplasmic membrane is more easily dissolved than the outer layers of the envelope, and (2) that there is a firm binding between DNA and the outer membrane in vivo.
Insights
Investigating Escherichia coli envelope components revealed that nuclear bodies are primarily composed of the outer membrane, with DNA firmly bound to it. This finding highlights the outer membrane
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Nuclear bodies in Escherichia coli are complex structures derived from cell lysis.
- Understanding their composition is crucial for deciphering bacterial cell structure and DNA organization.
Purpose of the Study:
- To investigate the envelope components of nuclear bodies from Escherichia coli W7.
- To determine the association of DNA with specific envelope layers.
Main Methods:
- Mild lysis of Escherichia coli W7 cells.
- Incorporation of 2,6-diaminopimelic acid (DAP) to label peptidoglycan.
- Lipid labeling with 3H-palmitic acid.
- Isopycnic centrifugation.
- Chloramphenicol treatment.
Main Results:
- Nuclear bodies contained approximately 14% of the cell's murein layer.
- Phosphatidylethanolamine was enriched in nuclear bodies compared to whole cells.
- DNA, peptidoglycan, and proteins were localized to the outer membrane.
- Cytoplasmic membrane components were more easily dissolved during lysis.
Conclusions:
- The outer membrane is the primary structural component of Escherichia coli nuclear bodies.
- DNA exhibits a strong in vivo association with the bacterial outer membrane.
- Differential lysis susceptibility of envelope layers influences the isolation of cellular components.