Abstract: Exopolysaccharides (EPS) produced from Pseudomonas syringae pv. tomato, P. syringae Davson 973 and P. syringae pv. coriandricola 908 were studied as affected by different types of culture media. The I.R. spectroscopy data of purified polysaccharides from these organisms were compared with authentic algal alginate sample. The results show presence of many functional groups in the obtained EPS which are: H- bonded hydroxyl group typical for polysaccharide (1050- 1100 and 3200-3600 nm) as well as C-H (at 1380-1450 cm and 2930 cm). The presence of bands at 2000-2800 nm region indicated the presence of free carboxyl groups. The spectrum showed a band at 948.5 nm, which assign to the C–O stretching vibration of uronic acid residues, and one at 888.3 nm assigned to the C1–H deformation vibration of β-mannuronic acid residues and also a band at 820.0 nm was detected. The obtained results indicate that purified EPSs from the tested organisms have great similarity with the authentic algal alginate sample. Thus, EPSs produced by P. syringae pv. tomato, P. syringae Davson 973 and P. syringae pv. coriandricola 908 could be identified as alginate.