Fluorescence-labeled wheat germ agglutinin binds specifically to N-acetylglucosamine in the outer peptidoglycan layer of gram-positive bacteria. The peptidoglycan layer of gram-negative bacteria is covered by a membrane and is not labeled by the lectin. By exploiting this phenomenon, an alternative Gram staining technique has been developed.

The Bacillus subtilis genome encodes 16 penicillin-binding proteins (PBPs), some of which are involved in synthesis of the spore peptidoglycan. The pbpI (yrrR) gene encodes a class B PBP, PBP4b, and is transcribed in the mother cell by RNA polymerase containing sigma(E). Loss of PBP4b, alone and in combination with other sporulation-specific PBPs, had no effect on spore peptidoglycan structure.