Peptidoglycan synthesis in bacilli

Abstract

A study has been made of the cycle of reactions involved in peptidoglycan synthesis in particulate preparations from Bacillus megaterium and Bacillus stearothermophilus and some of the properties of the system are described. The particulate enzyme preparation from B. megaterium is inactivated rapidly at 37° and to a lesser extent at 30°; the most sensitive reaction appears to be the dephosphorylation of C-55 isoprenoid alcohol pyrophosphate. It has not been established whether a thermosensitive enzyme is involved or whether disorganization of a lipid-protein complex takes place. The cycle of reactions in the particles from B. stearothermophilus is more stable to high temperatures; only 25% of the activity in the polymerisation reaction is lost in 2 h at 55°. The activity of a second enzyme, d,d-alanine carboxypeptidase, is unaffected after 3 h at 65°. The stability of this membrane-bound multi-enzyme system from B. stearothermophilus in vitro provides further evidence that the organism can survive at high temperatures without inactivation of its enzyme proteins and the consequent need to replace them.