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Toxic membrane fractions from Mycoplasma fermentans
Abstract:
A recent isolate of Mycoplasma fermentans (strain K10, from human leukemic bone marrow) induced a lethal toxicity syndrome in mice. High doses of both viable and inactivated cells were toxic when injected intraperitoneally. Whole lysates and membranes from osmotically shocked cells killed mice, but cytoplasm did not. When membranes were dissolved in detergents and reaggregated by dialysis in the presence of Mg(2+), the lipid-protein complex thus formed was toxic. Lipids extracted from membranes with chloroform-methanol did not kill mice. Protein-rich fractions (obtained by reaggregation plus acetone washes or ammonium sulfate precipitation of dissolved membranes) were also not toxic. No qualitative differences in proteins from three toxic isolates and three nontoxic laboratory strains of M. fermentans were detectable by polyacrylamide gel electrophoresis. The toxic factor contained in reaggregated membranes was heat-stable but sensitive to Pronase, trypsin, and lipase.
Insights
A Mycoplasma fermentans isolate caused lethal toxicity in mice. The toxic factor, located in reaggregated cell membranes, was a heat-stable lipid-protein complex, not lipids or proteins alone.
Area of Science:
- Microbiology
- Immunology
- Toxicology
Background:
- Mycoplasma fermentans is a bacterium known to cause various infections.
- Certain strains of Mycoplasma fermentans can induce toxic effects in mammalian hosts.
- Understanding the specific components responsible for Mycoplasma-induced toxicity is crucial for developing therapeutic strategies.
Purpose of the Study:
- To identify the component of Mycoplasma fermentans responsible for lethal toxicity in mice.
- To characterize the nature of the toxic factor present in the bacterium.
Main Methods:
- Induction of toxicity in mice using viable and inactivated Mycoplasma fermentans cells, lysates, membranes, cytoplasm, and extracted lipids.
- Detergent solubilization and Mg(2+)-mediated reaggregation of membrane components.
- Fractionation of membrane components using acetone washes and ammonium sulfate precipitation.
- Analysis of protein composition using polyacrylamide gel electrophoresis.
- Assessment of the toxic factor's stability to heat, Pronase, trypsin, and lipase.
Main Results:
- A specific isolate of Mycoplasma fermentans (strain K10) induced a lethal toxicity syndrome in mice.
- Whole cell lysates and isolated membranes were toxic, while cytoplasm was not.
- A toxic lipid-protein complex was formed when membranes were dissolved and reaggregated.
- Isolated lipids or protein-rich fractions were non-toxic.
- The toxic factor was heat-stable but degraded by Pronase, trypsin, and lipase, suggesting a protein component is involved.
Conclusions:
- The lethal toxicity induced by this Mycoplasma fermentans isolate is mediated by a heat-stable lipid-protein complex found in the cell membranes.
- Neither lipids nor proteins alone account for the observed toxicity.
- The toxic factor's sensitivity to proteases and lipase indicates a crucial role for protein in its activity.