Cell envelope of Neisseria gonorrhoeae CS7: peptidoglycan protein complex

Abstract

Treatment of cells grown to exponential phase with 4% sodium dodecyl sulfate for 3 h at 100 degrees C resulted in solubilization of all cellular components except for peptidoglycan. In most strains, cells cultured in liquid gonococcal broth at pH 7.2 yielded a peptidoglycan composed primarily of N-acetylmuramic acid N-acetylglucosamine, alanine, glutamic acid, and diaminopimelic acid in a molar ratio of 1:1:2:1:1. The peptidoglycan in these cells accounted for 1 to 2% (dry weight) of the cells. However, in cells cultured at pH 6.0, the dry weight of peptidoglycan increased to 4 to 13%. Preliminary investigations indicated that the apparent increase in weight is strain dependent and is due in part to associated protein(s). Neisseria gonorrhoeae strain CS7 had elevated amounts of protein associated with the peptidoglycan regardless of growth pH. The peptidoglycan-protein complex could not be dissociated by additional extraction with sodium dodecyl sulfate, 10 M LiCl2, or ethylenediaminetetraacetate or by 7.5% polyacrylamide gel electrophoresis. The complex could be degraded by lysozyme, trypsin, chymotrypsin, Pronase B, and Chalaropsis sp. muramidase.