The sugar analysis of the glycans of the type strains of marine proteobacteria of the genera Pseudoalteromonas and Marinomonas--Pseudoalteromonas atlantica IAM12927T, P. aurantia NCIMB 2033T, P. citrea ATCC 29719T, P. elyakovii KMM 162T, P. espejiana ATCC 29659T, P. piscicida NCIMB 645T, P. tetraodonis IAM 14160T, Marinomonas communis ATCC 27118T, and M. vaga ATCC 27119T--showed that they contain glucose, galactose, galactosamine, glucosamine, fucose, rhamnose, mannose, heptose, 2-keto-3-deoxyoctonate (KDO), uronic acids, colitose (3,6-dideoxyl-L-xylo-hexose), and 6-deoxy-L-talose. The carbohydrate composition of the antigenic polysaccharides (PSs) of P. elyakovii KMM 162T and P. espejiana ATCC 29659T depended on the type and the concentration of carbohydrate substrates in the nutrient media. The molar proportion between rhamnose, glucose, and galactose (ca. 1:0.3:2) in the PS of P. elyakovii KMM 162T was almost the same in the media lacking carbohydrates or containing glucose or galactose at a concentration of 1 g/l. At the same time, the molar proportion between fucose, glucose, galactose, galactosamine, and glucosamine (ca. 1:1:1:2:0.5) in the PS of P. espejiana ATCC 29659T depended on the presence and the concentration of carbohydrate substrates in the medium. A high concentration of glucose in the medium (30 g/l) brought about a rise in the content of glucose in PSs (9-fold for the PS of P. elyakovii KMM 162T and 4.6-fold for the PS of P. espejiana ATCC 29659T) and led to a decrease in the content of other carbohydrates. The cultivation of these two strains at a lactose concentration of 30 g/l resulted in their PSs containing glucose and galactose in about equal proportions (ca. 1:1 in the case of P. espejiana ATCC 29659T and ca. 2.1:1.7 in the case of P. elyakovii KMM 162T).