Immunogold Localization of p55-Fibril Protein and p25-Spiralin in Spiroplasma Cells

Transmission electron microscopy of thin sectioned cells of the honeybee spiroplasma BC3 revealed evidence of a helically twisted ribbon closely associated with the cytoplasmic surface of the plasma membrane. The cellular distribution of p55-ftbril protein as demonstrated by immunogold staining with anti-p55 antibody was consistent with the presence of p55 in this ribbon. We conclude that spiroplasma fibrils are arranged in a single helically twisted ribbon rather than forming a contractile sheath or branched axial fibre. Immunogold staining with anti-p25-spiralin antibody confirmed that this protein is localized in the plasma membrane and also showed that it occurs in ixtracellular strands. These strands may be antigenically distinct from the integral form of the protein.