Biology of prokaryotic probiotics

Bacteria and archaea are two distinct phyla of the prokaryotic kingdom containing many different species of microorganisms. Prokaryotic probiotics are single-celled nonnucleated organisms which when consumed live in adequate numbers confer a health benefit to the host. They can be classified based on morphology, ability to form spores, method of energy production, nutritional requirements, and reaction to the Gram stain. Currently, there are no known probiotic archaea but they have an important potential in the synthesis of prebiotics and other bioproducts due to their unique characteristics. There are however, probiotic bacteria mainly coming from the genera of Lactobacillus and bifidobacteria. Lactobacillus has 106 validly described species, out of which 56 species have probiotic potential. On the other hand, Bifidobacteria currently has 30 species validly described, with 8 having probiotic capabilities. A close study of these microorganisms reveal that probiotic bacteria are likely to be Gram positive, mostly rod shaped but with fewer spherically shaped ones, nonspore forming and nonflagellated bacteria.