DEFORMATIONS IN THE CYTOPLASMIC MEMBRANE OF ESCHERICHIA-COLI DIRECT THE SYNTHESIS OF PEPTIDOGLYCAN - THE HERNIA MODEL

To explain the growth of the Gram-negative envelope and in particular how it could be strengthened where it is weakest, we propose in the he rnia model that local weakening of the peptidoglycan sacculus allows t urgor pressure to cause the envelope to bulge outwards in a hernia; th e consequent local alteration in the radius of curvature of the cytopl asmic membrane causes local alterations in phospholipid structure and composition that determine both the synthesis and hydrolysis of peptid oglycan. This proposal is supported by evidence that phospholipid comp osition determines the activity of phospho-N-acetylmuramic acid pentap eptide translocase, UDP-N-acetylglucosamine: N-acetylmuramic (pentapep tide)-P-P-bactoprenyl-N-acetylglucosamine transferase, bactoprenyl pho sphate phosphokinase, and N-acetylmuramyl-L-alanine amidase. We also p ropose that the shape of Escherichia coli is maintained by contractile proteins acting at the hernia. Given the universal importance of memb ranes, these proposals have implications for the determination of shap e in eukaryotic cells.