PERMEABILITY OF THE OUTER-MEMBRANE OF BACTERIA

The outer membrane of Gram‐negative bacteria is an attractive system for the study of the structure‐function relationships in biological membranes. This membrane has, inter alia, the task of regulating the inflow of nutrients and outflow of waste products. Investigations with the aid of mutants showed that there are at least two general pathways for the diffusion of small molecules across the outer membrane: one for hydrophobic and one for hydrophilic compounds. In the case of the “hydrophobic pathway” the hydrophobic compound dissolves in the interior of the membrane and then crosses the membrane in accordance with the partition coefficient. In wild‐type forms of enteric bacteria this pathway cannot be used—presumably owing to the absence of regions with phospholipid bilayers. Small hydrophilic molecules, on the other hand, penetrate the membrane through water‐filled pores. Copyright © 1979 by Verlag Chemie, GmbH, Germany