Freeze etch morphology of outer membrane mutants of Escherichia coli K12.

Freeze etching showed that the loss of each of the major outer membrane proteins b, c or d in mutants of Escherichia coki K12 does not influence the morphology of fracture faces of the outer membrane. Mutants that possess a heptose-deficient lipopolysaccharide and which in addition are deficient in one or more major outer membrane proteins exhibit a reduction in the number of intramembranous particles of the outer membrane. Moreover it was shown that lipid phase transitions induce a lateral lipid protein separation in the outer membrane, similar to that found in the cytoplasmic membrane.