Structure of the cell wall of Bacillus species C.I.P. 76-111

Abstract

An unusual type of bacterial cell wall was encountered in a Bacillus strain referred to as Bacillus sp. C.I.P. 76-111. The major constituent of this cell wall is a high-molecular-weight anionic protein non-covalently associated to a peptidoglycan-polysaccharide complex. The cell wall appeared as a multilayered structure when sections of whole cells or of isolated cell walls fixed with glutaraldehyde and postfixed with osmium tetroxide were examined by electron microscopy. The correlation between the observed morphological features and the biochemical data suggested that a thin central electron-dense layer identifiable with the peptidoglycan-polysaccharide complex is located between two similar thick layers of protein. Furthermore, negative staining of isolated cell walls revealed that the outer protein layer has a regular surface array of subunits with hexagonal symmetry. Several structural properties of the cell wall peptidoglycan were investigated and were found to resemble those of other bacilli. Further characterization of the autolytic system showed that an N-acetylmuramyl-L-alanine amidase and a glycosidase, presumably a N-acetylmuramidase, were associated with the peptidoglycan-polysaccharide complex. It was also established that this strain is devoid of membrane teichoic acid.