The envelope structure of Branhamella catarrhalis as studied by transmission electron microscopy

The envelope structure of Branhamella catarrhalis was studied by electron microscopy and compared with that of other bacteria of the family Neisseriaceae, such as Moraxella lacunata subsp. liquefaciens and Neisseria gonorrhoeae. Negative staining of B. catarrhalis showed a mamilliform surface similar to that of Moraxella. On thin sections, the cell wall appeared to be made up of a wavy outer membrane tightly linked to a straight peptidoglycan layer. Spicule-like structures protruded from the cell surface. Ruthenium red staining revealed that they contained polysaccharides. While the outer polysaccharide layer of N. gonorrhoeae was unstable after repeated subcultures in vitro, this layer remained stable in B. catarrhalis and in Moraxella lacunata subsp. liquefaciens.