The ability of an exopolymer of glycoproteic character (GP) excreted by a new Gram-negative species Pseudoalteromonas antarctica NF3, to coat phosphatidylcholine (PC) liposomes and to protect; these bilayers against the action of the sodium dodecyl sulfate (SDS) surfactant was investigated. Transmission electron microscopy micrographs of freeze fractured liposome/GP aggregates reveal that the addition of GP to liposomes led to the formation of a film (polymer adsorbed onto the bilayers) that tightly coated PC bilayers. The complete coating was achieved at a PC:GP weight ratio of about 9:1. Higher GP amounts resulted in a growth of this film, which exhibited at the highest GP proportion (50% of GP in weight) a multilayered structure. An increasing resistance of PC liposomes to be affected by SDS at both subsolubilizing and solubilizing levels occurred as the proportion of GP in the system rose, although this protective effect was more effective at low GP proportions (PC:GP weight ratios from 9:1 to 8:2). Although a direct dependence was found between the growth of the enveloping structure and the resistance of the coated liposomes to be affected by SDS, the best protection occurred when this structure was a thin film (thickness of about 20-25 nm for a PC:GP weight ratio ranging from 9:1 to 8:2).