The taxonomic position and biological activities of two Bacillus strains used in veterinary probiotics were studied in this work. These microorganisms inhibit growth of a broad spectrum of pathogenic cultures. They synthesize proteolytic enzymes and other biologically active metabolites, and to some extent, supplement each other with probiotic activities. It is not clear whether these versatile activities are properties of individual strains or bacterial taxa as whole. 16S rRNA comparisons were conducted and illustrated the relatedness of these strains to Bacillus amyloliquefaciens . Their cell wall fatty acid contents were consequently analysed and specified a relation to the " Bacillus velezensis " ecomorph. On account of the previous observations, a simple method of 16S rRNA profiling by polymorphic nucleotides was proposed to determine a group of organisms closely related to "B. velezensis" and B. amyloliquefaciens subsp. plantarum, for they are biologically active strains suitable for use in biotechnology. The extreme genetic plasticity of these bacteria endowed each strain with a unique spectrum of antagonistic activity.