EN
The data presented in this article were obtained from studies on the effect of pseudomonads on the growth and development of legume plants and on their symbiosis with Rhizobium and Bradyrhizobium. The conducted investigations have proven that pseudomonads are typical microorganisms in the rhizosphere of cultivated plants and show root colonization ability. The effectiveness of the root colonization depends on: the chemical composition of root exudates and their chemotaxic properties; the mobility of the Pseudomonas bacteria cells; the reaction between polysaccharides on the bacterial cell surface and glycoproteins in the surface of the roots; competition abilities of the bacterial strains; soil properties and many other factors. It has been proved that pseudomonads can stimulate, inhibit or show no effect on the development and yield of the host plant. The means by which the bacterial strains can influence plant development depends on the kind and concentration of metabolites produced by the tested strain and the properties of the plant. The mechanism of positive effect of pseudomonads on the plant is the protection of the host plant against its pathogens, due to the abllity of bacteria to produce siderophores (especially of the pseudobactin-pioverdin group) and antibiotics. Some representatives of Pseudomonas can mobilize phosphate ions from poorly soluble inorganic compounds and can release growth stimulators and vitamins. Among the pseudomonads are many phytopathogenic strains as well as many strain negatively influencing plant growth without visible symptoms of disease. This negative influence could be the result of disturbances in the supply to the plant of nutrients and growth stimulators caused by pseudomonads negatively affecting the soll microorganisms from the PGPR group and stimulating microorganisms from the DRMO group.