Freeze-fracture confirmation of the presence of a core in the specialized tip structure of Mycoplasma pneumoniae

Abstract

The presence of a specialized terminal region in Mycoplasma pneumoniae was seen in thin sections viewed in an electron microscope. Actively growing cells were examined by the freeze-fracture technique in the absence of fixation to further establish the core as a significant structural entity. Cross fractures revealed a cytoplasmic matrix surrounding a central core structure of about 54 nm. This structure disappeared rapidly in aging cells. The convex protoplastic faces of the membrane around the core had characteristic 5-to 10-nm intramembrane particles evenly distributed across the cell surface, with no apparent difference in the region of the specialized tip. A periodicity previously noted in negatively stained preparations was clearly defined here in thin sections. Attachment of actively growing cells to sheep erythrocytes was seen primarily as a side attachment rather than attachment at the tip alone. This association between the mycoplasma and the sheep erythrocytes seriously deformed the sheep erythrocytes, but no membrane fusion could be detected.

Mycoplasma pneumoniae cytadherence phase-variable protein HMW3 is a component of the attachment organelle

“…The linear pattern of gold labeling (Fig. 2) may contribute to the periodicity observed by others in the core structure and terminal knobs (22,33). Immunogold labeling of thin-sectioned ( Fig.…”

“…Individual triton shells exhibit a rodlike structure that terminates in a knob formation at one end and a meshwork of fibers at the other end (10,22). Examination of thin sections of filamentous M. pneumoniae by transmission electron microscopy likewise reveals an electron-dense core extending the length of the attachment organelle (8,13,33,34). The core structure has a striated appearance or periodicity, suggesting that it contains repeating subunits (22,33).…”

“…Examination of thin sections of filamentous M. pneumoniae by transmission electron microscopy likewise reveals an electron-dense core extending the length of the attachment organelle (8,13,33,34). The core structure has a striated appearance or periodicity, suggesting that it contains repeating subunits (22,33). Furthermore, the core structure terminates in a knob formation at one end and has fibers extending from the opposing base into the matrix of the cell body (3,33,34), which is similar in appearance and organization to the triton shell (22).…”

“…The core structure has a striated appearance or periodicity, suggesting that it contains repeating subunits (22,33). Furthermore, the core structure terminates in a knob formation at one end and has fibers extending from the opposing base into the matrix of the cell body (3,33,34), which is similar in appearance and organization to the triton shell (22).…”

Electron Microscopic Studies on the Attachment of Mycoplasma pulmonis to Mouse Synovial Cells Cultured In Vitro

“…They concluded that the attach mentoccurred via the tip of the mycoplasma. On the other hand, Wall et al (14) reported that the attachment of M. pneumoniae to erythrocytes neither initially nor necessarily involved the tip structure and the tip structure did not appear to serve as an attachment organ. Boatman et al (3), using both transmission and scanning electron microscopes, studied attachment of bovine mycoplasmas to HeLa cells.…”