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

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.