Related Experiment Videos
Adherence of Mycoplasma gallisepticum to human erythrocytes
Abstract:
Pathogenic mycoplasmas adhere to and colonize the epithelial lining of the respiratory and genital tracts of infected animals. An experimental system suitable for the quantitative study of mycoplasma adherence has been developed by us. The system consists of human erythrocytes (RBC) and the avian pathogen Mycoplasma gallisepticum, in which membrane lipids were labeled. The amount of mycoplasma cells attached to the RBC, which was determined according to radioactivity measurements, decreased on increasing the pH or ionic strength of the attachment mixture. Attachment followed first-order kinetics and depended on temperature. The mycoplasma cell population remaining in the supernatant fluid after exposure to RBC showed a much poorer ability to attach to RBC during a second attachment test, indicating an unequal distribution of binding sites among cells within a given population. The gradual removal of sialic acid residues from the RBC by neuraminidase was accompanied by a decrease in mycoplasma attachment. Isolated glycophorin, the RBC membrane glycoprotein carrying almost all the sialic acid moieties of the RBC, inhibited M. gallisepticum attachment, whereas asialoglycophorin and sialic acid itself were very poor inhibitors of attachment. Only part of the (125)I-labeled glycophorin bound to mycoplasmas could be removed by neuraminidase or by exchange with unlabeled glycophorin. It is suggested that glycophorin, representing the isolated major RBC receptor for M. gallisepticum, binds to the mycoplasmas both specifically, through its sialic acid moieties, and nonspecifically, through its exposed hydrophobic polypeptide moiety.
Insights
Pathogenic mycoplasmas like Mycoplasma gallisepticum use specific receptors on red blood cells (RBCs) for attachment. Glycophorin, an RBC membrane protein, acts as a key receptor, binding mycoplasmas via sialic acid and hydrophobic interactions.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Pathogenic mycoplasmas colonize respiratory and genital tracts.
- Understanding mycoplasma adherence is crucial for studying infections.
Purpose of the Study:
- To develop a quantitative system for studying mycoplasma adherence.
- To identify the specific receptors involved in Mycoplasma gallisepticum attachment to host cells.
Main Methods:
- Developed an experimental system using labeled Mycoplasma gallisepticum and human erythrocytes (RBCs).
- Quantified mycoplasma attachment by measuring radioactivity.
- Utilized pH, ionic strength, temperature, and enzymatic treatments (neuraminidase) to analyze binding.
- Investigated the role of isolated RBC membrane components, including glycophorin.
Main Results:
- Mycoplasma gallisepticum attachment to RBCs was influenced by pH, ionic strength, and temperature.
- Attachment kinetics followed first-order reactions, indicating specific binding sites.
- Neuraminidase treatment and removal of sialic acid residues reduced mycoplasma attachment.
- Isolated glycophorin significantly inhibited attachment, suggesting it as the primary RBC receptor.
- Evidence suggests both specific (sialic acid) and nonspecific (hydrophobic) binding interactions between glycophorin and mycoplasmas.
Conclusions:
- Glycophorin is identified as the major RBC receptor for Mycoplasma gallisepticum.
- Mycoplasma gallisepticum employs a dual binding mechanism involving sialic acid and hydrophobic interactions with glycophorin.