PEPTIDOGLYCAN SYNTHESIS AND ITS FINE CHEMICAL-COMPOSITION IN DIVIDINGAND NOT DIVIDING KLEBSIELLA-PNEUMONIAE COCCI

Peptidoglycan synthesis and its fine chemical composition were studied in dividing and in non-dividing Klebsiella pneumoniae cocci and compa red with rods. The beta-lactam mecillinam, a specific inhibitor of lat eral wall elongation which causes rod-to-sphere transition in rods, sh owed 50% inhibition of the peptidoglycan in normal rods of the parent Mir A12 only if added at an early stage of the cell cycle and no effec t if added later or during septation. In the rods of the mutant Mir M7 , mecillinam was shown to inhibit 50% of peptidoglycan synthesis until rods become cocci, and thereafter to be absolutely devoid of effects. On the contrary, piperacillin, a specific inhibitor of septum formati on, was active on all strains regardless of their cell shape, only if added at 20 and removed at 40 min of the cell cycle. As regards the an alysis of peptidoglycan fine chemical composition, bacteria dividing a s cocci showed alterations in the muropeptide composition consisting i n a 50-fold increase in the tetramer family. This alteration was not s een in the cocci that did not divide as such. These results confirm ou r previous claim that septum formation and lateral wall elongation are mutually exclusive in normal rods and that septum formation requires the synthesis of a peptidoglycan of different chemical composition.