ULTRASTRUCTURE AND BIOCHEMISTRY OF THE CELL-WALL OF PROCHLOROTHRIX-HOLLANDICA (PROCHLORACEAE)

The ultrastructure of the outer membrane of Prochlorothrix hollandica was studied by freeze-fracture electron microscopy. The exoplasmic surface was found to be covered with a network of fine fibrils. The plasmic fracture face had a fibrillar appearance and presented a pattern of densely packed globular particles, which were correlated in size and distribution with the corresponding particles of the exoplasmic fracture face. Major outer membrane proteins (M(r) 56,000 and 59,000) were found to be strongly associated with the peptidoglycan layer. Isolated lipopolysaccharide formed highly ordered aggregates in aqueous dispersion and contained glucosamine, the 3-hydroxy fatty acids (3-OH-14:0, iso-3-OH-15:0, 3-OH-16:0) in addition to O-specific neutral sugars (Glc, Rha, Fuc, Gal, Man, Xyl, 3-O-methyl-xylose). A peptidoglycan-polysaccharide complex in the cell wall of Prochlorothrix hollandica was composed of directly cross-linked A1-gamma-type peptidoglycan and a polysaccharide moiety (GlcN, ManN, Glc, Man) covalently linked to muramic acid-6-phosphate as the binding site.