Physicochemical properties of PM-factor, a surface-active agent produced by Pseudomonas marginalis

An extracellular surface-active agent, PM-factor, was obtained by high-speed centrifugation from the culture broth of Pseudomonas marginalis PD-14B. PM-factor exhibited emulsifying activity on a broad spectrum of hydrocarbon liquids, including aromatics, aliphatics, crude oil, and creosote. The factor appeared as ball-shaped particles of varying diameter when examined by electron microscopy (0.16-1.4 mu m). Gel filtration chromatography demonstrated a high molecular mass of the factor (>10(6) Dal. The ultraviolet absorption spectrum manifested a peak in the region 200 nm rather in the region 260-280 nm. Amino acid analysis showed a very low amount of aromatic amino acids residues in the protein moiety of PM-factor. The presence of 3-deoxy-D-mannooctulosonic acid, heptose, hexosamine, phosphorus, and 3-hydroxy fatty acid indicated that PM-factor contained lipopolysaccharide. The emulsifying activity of PM-factor was inhibited strongly by mercuric chloride and moderately by EDTA. Polymyxin B, Ca2+, and Mg2+ markedly stimulated the factors emulsifying activity. Roles of the bioemulsifier in the functioning of P. marginalis as a plant pathogen and in bioremediation are discussed.