Isolation and characterization of outer and cytoplasmic membranes from spheroplasts of Acetobacter aceti.

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Abstract
The spheroplast membrane of Acetobacter aceti IFO 3284 was separated into outer and cytoplasmic membranes by alkaline sucrose density gradient centrifugation after treatment of the cells with lysozyme in sucrose-EDTA, pH 8.0. The cytoplasmic membrane, which was transparent and red colored, showed a specific gravity of 1.15 g/ml, and a number of protein components. High contents of heme b and heme c, and high enzyme activities of various membrane-bound primary dehydrogenases, which are characteristics of acetic acid bacteria, were found in the cytoplasmic membrane fraction. On the other hand, the outer membrane, which was white and turbid when homogenized, exhibited a high content of 2-keto-3-deoxyoctonate, and only four major polypeptides were observed on SDS-polyacrylamide gel electrophoresis. The outer membrane showed a specific gravity of 1.25 g/ml due to its high lipopolysaccharide content. A predominant species of the outer membrane proteins, tentatively designated as A1, was found to be heat-modifiable in SDS solution. The A1 peptide on SDS-polyacrylamide gel showed varied migration, from a position corresponding to 31, 000 daltons to one of 37, 000 daltons, when heated at over 60°C and then subjected to gel electrophoresis.

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