This morphogenetic effect of penici

This morphogenetic effect of penicillin can be demonstrated by growing either Gram-positive or Gram-negative bacteria in the presence of sub-lethal concentrations of penicillin. The images below show Gram-stained cells of Bacillus cereus that had been cultured in the absence of penicillin (left-hand image) or in the presence of a low concentration of the penicillin derivative termed Ampicillin (right-hand image). By affecting the cross-linking of the bacterial cell wall, penicillin has caused the bacterium to grow as larger cells with less frequent cell divisions.