Comparison of potentially pathogenic free-living amoeba hosts by Legionella spp. in substrate-associated biofilms and floating biofilms from spring environments

► The lower pathogenic virulence Naegleria was easily found in biofilms. ► Hartmanella vermiformis plays a role in the survival of FLA-intracellular Legionella. ► Acanthamoeba in biofilms should be considered a potential health threat.