Full text loading...
Chapter 10 : Mycoplasma pneumoniae Attachment and Colonization of the Respiratory Mucosa
Category: Bacterial Pathogenesis
Mycoplasmas are remarkable bacteria distinguished most notably by the complete lack of a cell wall, which is reflected by their grouping in the taxonomic class Mollicutes. Mycoplasma pneumoniae infections are typically transmitted by the aerosol route, with the most common manifestations being bronchitis and atypical, or “walking,” pneumonia. Extrapulmonary consequences are reported for about 25% of M. pneumoniae infections. The small size and minimal genome of M. pneumoniae belies an unexpectedly complex cellular architecture that includes a novel cytoskeleton and a differentiated polar structure, or terminal organelle. By combining mutant analysis with the digital imaging of growing cultures, significant headway is being realized in assigning functions to certain terminal organelle components with respect to gliding motility and cell development. As the leading end in gliding motility, the terminal organelle is likely to initiate the recognition and binding of host cell receptors. The authors speculate that gliding motility may contribute to M. pneumoniae colonization and pathogenesis in the respiratory tract in at least three ways. Researchers have begun to utilize a normal human bronchial epithelial (NHBE) cell model system to explore directly the interaction of M. pneumoniae cells with the mucosal epithelium in the early stages of infection. The reduced attachment to NHBE cells by the P200 mutant makes a compelling, though not definitive, case for a role for gliding motility in the colonization of the respiratory mucosa.
Scanning electron micrograph of M. pneumoniae cells. Arrows, terminal organelle; bar, 1.0 μm. Photo courtesy of S. R. Bose.
Schematic illustration of airway epithelium. Ciliated, goblet, and basal cells are indicated, as are the mucus and periciliary layers of the airway surface liquid.
Laser confocal microscopy image of M. pneumoniae-infected NHBE cells. NHBE cells were incubated with wild-type M. pneumoniae for 30 min, washed, and probed with antibodies to tubulin to indicate cilia and M. pneumoniae-specific antibodies. Mycoplasmas are seen as fluorescent spots which are associated primarily with the ciliated cells. Bar, 20 μm.
Representative mycoplasma diseases in domestic animals, wildlife, and humans a
Comparison of gliding velocities and attachment to glass, erythrocytes, and NHBE cells by wild-type M. pneumoniae and P30 and P200 mutants a