The ability of 23 endophytic Bacillus subtilis strains to mobilize sparingly soluble mineral and organic phosphates in vitro has been researched. Detection of such activity and its ratio has been shown to be depended on the methods used. When solid medium with insoluble phosphates has been used most of strains solubilized iron phosphate better than the others. In experiments with liquid media the best mobilization of calcium phosphate has been observed but bacteria didn't solubilize iron and aluminium phosphates except a few strains. Some strains displayed phosphatase activity so one can assume their ability to degrade organic phosphorus compounds. For the first time we advance a hypothesis that phosphate solubilization could be one of the factors reducing the efficiency of endomycorrhiza fungi competition with phosphate-mobilizing endophytic bacteria colonizing internal plant tissues. Wheat grain treatment with endophytic phosphate-mobilizing strains has been shown to reduce some parameters of root mycorrhization confirming authors' hipothesis.