Morphology of sulfur granules produced by Pseudomonas aeruginosa in cows.

A sulfur granule produced by Pseudomonas aeruginosa in three cows was studied light- and electron-microscopically. It consisted of clumps of basophilic bacteria and eosinophilic clubs. The clubs radiated from the periphery outward. The bacteria were stained dark red by both PAS and MacCallum-Goodpasture staining. Electron-microscopically, the sulfur granule consisted of electron-dense amorphous material and bacteria. The intact bacterium was about 0.45 micrometers in diameter and had an electron-dense cell wall 15 nm in width. Beneath the cell wall, moderately electron-dense fine granular material was present. The center of the bacterium was electron lucent. The club was electron-dense amorphous material. Degenerative bacteria and pilus-like structures were often seen in it. In one case, clusters of bacteriophages were present in and near the degenerative bacteria. Their head was hexagonal and 40 nm in diameter.