<Li> Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD - transpeptidase . </Li> <Li> A much smaller volume of periplasm than that in Gram - negative bacteria . </Li> <P> Only some species have a capsule, usually consisting of polysaccharides . Also, only some species are flagellates, and when they do have flagella, have only two basal body rings to support them, whereas Gram - negative have four . Both Gram - positive and Gram - negative bacteria commonly have a surface layer called an S - layer . In Gram - positive bacteria, the S - layer is attached to the peptidoglycan layer . Gram - negative bacteria's S - layer is attached directly to the outer membrane). Specific to Gram - positive bacteria is the presence of teichoic acids in the cell wall . Some of these are lipoteichoic acids, which have a lipid component in the cell membrane that can assist in anchoring the peptidoglycan . </P> <P> Along with cell shape, Gram staining is a rapid method used to differentiate bacterial species . Such staining, together with growth requirement and antibiotic susceptibility testing, and other macroscopic and physiologic tests, forms the full basis for classification and subdivision of the bacteria (e.g., see figure and pre-1990 versions of Bergey's Manual). </P>

What is the composition of both gram positive and gram negative cell walls