Electron cryotomography of Mycoplasma pneumoniae mutants correlates terminal organelle architectural features and function

• Published in: Molecular microbiology Vol. 108; no. 3; pp. 306 - 318
• Main Authors: Krause, Duncan C., Chen, Songye, Shi, Jian, Jensen, Ashley J., Sheppard, Edward S., Jensen, Grant J.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-05-2018
• Subjects: Adhesins, Bacterial - genetics; Adhesins, Bacterial - metabolism; Architecture; Assembly; Bacterial Adhesion - genetics; Bacterial Proteins - metabolism; Electron Microscope Tomography - methods; Electrons; Gliding; Knobs; Mitochondrial DNA; Mutants; Mycoplasma pneumoniae; Mycoplasma pneumoniae - genetics; Mycoplasma pneumoniae - physiology; Organelles - genetics; Organelles - metabolism; Phenotypes; Proteins; Substructures
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13937

Summary
The Mycoplasma pneumoniae terminal organelle functions in adherence and gliding motility and is comprised of at least eleven substructures. We used electron cryotomography to correlate impaired gliding and adherence function with changes in architecture in diverse terminal organelle mutants. All eleven substructures were accounted for in the prkC, prpC and P200 mutants, and variably so for the HMW3 mutant. Conversely, no terminal organelle substructures were evident in HMW1 and HMW2 mutants. The P41 mutant exhibits a terminal organelle detachment phenotype and lacked the bowl element normally present at the terminal organelle base. Complementation restored this substructure, establishing P41 as either a component of the bowl element or required for its assembly or stability, and that this bowl element is essential to anchor the terminal organelle but not for leverage in gliding. Mutants II‐3, III‐4 and topJ exhibited a visibly lower density of protein knobs on the terminal organelle surface. Mutants II‐3 and III‐4 lack accessory proteins required for a functional adhesin complex, while the topJ mutant lacks a DnaJ‐like co‐chaperone essential for its assembly. Taken together, these observations expand our understanding of the roles of certain terminal organelle proteins in the architecture and function of this complex structure.
Mycoplasma pneumoniae mutants defective in adherence and gliding were analyzed by electron cryotomography for corresponding changes in terminal organelle architecture. Ultrastructural changes ranged from complete loss of all eleven terminal organelle substructures in some mutants, to changes in specific substructures such as the protein knobs on the terminal organelle surface (green) or the bowl substructure (purple) at its base. Somewhat surprisingly, for other mutants no differences in terminal organelle architecture were evident.