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The external polysaccharide is a major component of Micrococcus lysodeikticus cell wall and displays distinct composition. The complete structure of the external polysaccharide had been elucidated as a basis for investigation of the cell wall structure-function relation. However, the mode of attachment of the polysaccharide to the peptidoglycan through a phosphodiester was not clear due to limitations in structural and biosynthetic studies. The present study describes purification of a lysozyme-resistant nondialyzable high-molecular-weight fragment of cell wall and identifies the sugar, D-glucose, as the point of external polysaccharide attachment to the peptidoglycan through a phosphate diester. Kinetic studies for the acid-catalyzed release of external polysaccharide from the peptidoglycan were performed in parallel with synthetic [methyl-2-acetamido-3-O-(D-1-carboxyethyl)-2-deoxy-alpha-D- glucopyranoside-6-yl]-alpha-D-glucopyranosyl phosphate and alpha-D-glucopyranosyl phosphate and showed the presence of a phosphodiester linkage between external polysaccharide and peptidoglycan. In addition, type of phosphate residue and cross-linking between muramic acid and protein part have been determined.

The occurrence of a specific high potential iron-sulfur protein in a halophilic, denitrifying coccus provisionally assigned to the genus Paracoccus has been confirmed through primary structure determination. This protein, known as "HiPIP", has been found previously only in photosynthetic bacteria. The sequence of this 71-residue protein is as similar to the HiPEPs from photosynthetic bacteria as they, in turn, are to one another (average number of identically matching residues is 38%). Paracoccus HiPIP is a highly acidic protein in accord with general observations on the proteins of halophilic bacteria. A possible explanation for its occurrence in Paracoccus is that gene transfer is involved.

Ghosts of Micrococcus lysodeikticus contain a mannan that is not removed by intensive washing procedures. Purified mannan, isolated by extraction of whole cells with hot, aqueous phenol, binds to membranes in vitro. Mannan also binds to DEAE-cellulose and migrates toward the anode in neutral and sodium dodecyl sulfate disc gel electrophoresis. In aqueous solution mannan has an apparent molecular weight of 10-6, but in the presence of sodium dodecyl sulfate its apparent molecular weight is 50,000 to 100,000; removal of the detergent results in reaggregation. Purified mannan contains mannose, succinate, fatty acid, and glycerol in a ratio of 50:4.9:2.1:1.0. Treatment of mannan with mild base produces a neutral, hydrophilic polysaccharide of relatively low molecular weight that has no affinity for membranes. At least 90% of the reducing termini are blocked in a base-stable linkage. Based on these results a tentative structure is proposed for the mannan.