Mycoplasmal adherence with particular reference to the pathogenicity of Mycoplasma pulmonis

Various eucaryotic cells adhere to colonies of some mycoplasmas (adsorption). The chemical nature of the receptors on the cells is not the same for all mycoplasma species, nor are the binding sites on different mycoplasmas the same. Some receptors comprise sialic acid, but in the case of Mycoplasma pulmonis, for example, attachment to cells is not mediated in this way. Nevertheless, adherence seems to be an important factor in the pathogenicity of this mycoplasma. Strain JB caused pneumonia in mice when inoculated intranasally, and colonies of this strain on agar absorbed erythrocytes (hemadsorption) strongly. After multiple passes in mycoplasma liquid medium, the strain lost its hemadsorbing capacity and also its mouse virulence, suggesting that the ability to attach to cells is virulence factor. Examination by electron microscopy of the virulent mycoplasma and its induced avirulent form after ruthenium-red staining showed that the stain was less thick on the surface of the avirulent form. In addition, the protein pattern of the avirulent mycoplasma, demonstrated by polyacrylamide gel electrophoresis, was deficient in three bands. These observations suggest that a glycosylated protein may form the binding site on M. pulmonis organisms that mediates their attachment to cells.