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Characterization of a Mycoplasma pneumoniae hmw3 mutant: implications for attachment organelle assembly
Melisa J Willby1, Duncan C Krause
1Department of Microbiology, University of Georgia, Athens, Georgia 30602, USA.
Abstract:
The proteins required for adherence of the pathogen Mycoplasma pneumoniae to host respiratory epithelial cells are localized to a polar structure, the attachment organelle. A number of these proteins have been characterized functionally by analysis of noncytadhering mutants, and many are components of the mycoplasma cytoskeleton. Mutations in some cytadherence-associated proteins have pleiotropic effects, including decreased stability of other proteins, loss of adherence and motility, and abnormal morphology. The function of protein HMW3, a component of the attachment organelle, has been difficult to discern due to lack of an appropriate mutant. In this paper, we report that loss of HMW3 resulted in decreased levels and more diffuse localization of cytoskeletal protein P65, subtle changes in morphology, inability to cluster the adhesin P1 consistently at the terminal organelle, reduced cytadherence, and, in some cells, an atypical electron-dense core in the attachment organelle. This phenotype suggests a role for HMW3 in the architecture and stability of the attachment organelle.
Insights
Loss of Mycoplasma pneumoniae protein HMW3 disrupts the attachment organelle, affecting cytoskeletal protein P65 localization and pathogen adherence to host cells. This suggests HMW3 is crucial for organelle architecture and stability.
Area of Science:
- Microbiology
- Cell Biology
- Structural Biology
Background:
- Mycoplasma pneumoniae adheres to host cells via proteins in its attachment organelle.
- Cytoskeletal proteins are vital for mycoplasma adherence, motility, and morphology.
- The function of HMW3 in the attachment organelle remained unclear due to a lack of suitable mutants.
Purpose of the Study:
- To investigate the function of protein HMW3 in Mycoplasma pneumoniae adherence.
- To elucidate the role of HMW3 in the structure and stability of the attachment organelle.
Main Methods:
- Generated and analyzed a Mycoplasma pneumoniae mutant lacking HMW3.
- Assessed changes in cytoskeletal protein P65 localization and P1 adhesin clustering.
- Evaluated effects on cell morphology, cytadherence, and attachment organelle structure using electron microscopy.
Main Results:
- HMW3 deletion led to reduced P65 levels and altered P65 distribution.
- Inability to consistently cluster P1 adhesin at the terminal organelle.
- Observed subtle morphological changes and reduced cytadherence, with some cells showing an abnormal electron-dense core in the attachment organelle.
Conclusions:
- Protein HMW3 plays a significant role in maintaining the architecture and stability of the Mycoplasma pneumoniae attachment organelle.
- HMW3 is essential for proper cytoskeletal organization and adhesin localization, impacting cytadherence.