Killing of Escherichia coli by a granulocyte fraction occurs without recognizable ultrastructural alterations in the bacterial envelope, as studied by freeze-fracture electron microscopy.

Concentrations of a highly purified rabbit polymorphonuclear leukocyte fraction that rapidly caused irreversible loss of viability of Escherichia coli (S15) but reversible envelope alterations produced no recognizable morphological changes as studied by freeze-fracture electron microscopy. These findings support previous evidence that the killing of certain gram-negative microorganisms by granulocyte fractions occurs with minimal structural or functional disorganization of cytoplasmic and outer membranes.