The invention relates to strains of a microorganism from the species Ensifer adhaerens having nematicidal activity against Meloidogyne javanica and to methods for obtaining a biomass of said microorganisms. The invention also provides methods for biologically controlling nematodes and for treating and preventing plant infection caused by nematodes based on the use of a microorganism from the species Ensifer adhaerens or of phytosanitary products obtained therefrom.