Purification and properties of biologically active factors in lipid extracts of Listeria monocytogenes

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Abstract
Lipid extracts of Listeria monocytogenes, capable of producing monocytosis and lymphopenia in mice, were fractionated by column chromatography on acid-treated Florisil. The biological activity was associated with a phospholipid fraction and further separation of this fraction by thin-layer chromatography indicated that most of the activity was in the slower running components which gave a positive reaction with ninhydrin. Water-soluble ninhydrin-positive material was separated from either the crude lipids or the phospholipid fractions by techniques such as a Folch wash, chromatography on Sephadex, or dialysis of a chloroform solution of the lipids against water. These water-soluble materials were also able to produce monocytosis and lymphopenia in mice, but the remaining phospholipid was still ninhydrin-positive and biologically active. Most of the water-soluble material was dialyzable, but the biological activity appeared to be concentrated largely in the non-dialyzable fraction. This fraction contained protein, and digestion with Pronase appeared to enhance the biological activity and to make the active material more readily dialyzable. Extraction of the lipid-extracted bacterial residue with saline yielded additional non-dialyzable water-soluble material with activity comparable to that shown by the lipid extracts.

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