Intracytoplasmic membrane production inEscherichia coli O111a₁: Isolation and lipid characterization of cell membranes

Abstract

The temperature-sensitive mutantEscherichia coli O111a₁ produces intracytoplasmic membrane when grown at temperatures above 37°C. Cytoplasmic and outer membrane were isolated from stationary-phase cells of 30°C- and 42°C-grown cultures ofE. coli O111a₁ (temperature-sensitive mutant) andE. coli O111a₁∶B₄ (control strain). A phospholipid (mg) to protein (mg) ratio of 1.21 was found for the cytoplasmic, including intracytoplasmic, membrane of 42°C-grown mutant cells, in contrast to 0.61 for the control strain. An enrichment of succinate dehydrogenase activity was also observed. The phospholipids were essentially identical (qualitatively and quantitatively) for both cultures at both temperatures.E. coli O111a₁ lost the ability to regulate the saturation/unsaturation of 16-carbon fatty acid, and accumulated increased quantities of β-OH myristate at 42°C. The density of the cytoplasmic membrane, including intracytoplasmic membrane, ofE. coli O111a₁ was elevated at 42°C to 1.218 g/cm³.