Algal alginates are of great importance for industrial applications. Since their properties depend on the kind of algae and the time of harvesting, supply problems caused price fluctuations. Hence, current research focuses on alternative alginate sources. Back in the 60s, exopolysaccharides similar to algal alginates were found. They were produced by mucoid Pseudomonas aeruginosa strains which embed themselves in a slime matrix containing bacterial alginates. The focus of this thesis was a comparisons of the physico-chemical properties of bacterial and algal alginates. The main results of the performed investigations are as follows: a) both substances aggregate in highly diluted solutions, b) bacterial alginates have a bigger molar mass than algal alginates, c) their mean squared radii of gyration are bigger than those of algal alginates, d) the second osmotic virial coefficients of these systems are negative and temperature dependent, e) acetylation of alginates support the aggregation, f) bacterial alginate do not gel analog to the egg box mechanism.