Bacillus species are a group of saprophytic Gram-positive, rod shaped, spore-forming aerobic or facultatively anaerobic bacteria. They are commonly found in soil, water, dust, air and food products of plant origin. Some strains can also be found in the normal gut microflora. The genus Bacillus is in fact closely related to Lactobacillus spp., with both belonging to the phylum Firmicutes. Of the hundred species contained in the Bacillus genus, only a select few are used as probiotics, including: Bacillus subtilis, Bacillus coagulans, Bacillus clausii included in Proflora® 4R.