Electrokinetical Studies on Bacterial Surfaces

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Abstract
The distinctive elec-trophoretic response of lipids in the presence of anionic surface-active agents, shown by expts. on known substances, was used to detect lipids at the surface of bacterial cells. The amt. of lipid in the surface of cells of both Micrococcus aureus and Mycobacterium smegmatis could be altered, within limits, by varying the conditions of growth. Other bacteria, such as some bacilli, did not produce surface lipids. Much of the surface lipid of Micrococcus aureus could be removed by extraction with hot alcohol but not with ether. It was removed by lipase without killing the cells, and small amts. of fatty acids were recovered from the supernatant after the lipase treatment. Amphoteric material in the surface of M. aureus, distinct from the lipid, was detected by change in mobility with pH. Its occurrence also depended on the growth conditions, and it could be removed from living cells with trypsin. Lipase and trypsin were not effective in removing the lipid or the polar groups from the surface of cells of Mycobacterium smegmatis. Some of the properties of the cell surface of Micrococcus aureus remaining after lipase and trypsin treatment, and the intensity of acid hydrolysis necessary completely to break down the cell wall of several bacteria, were detd.