Definition of Minimal Standards for the accurate taxonomic description and identification of species belonging to Bifidobacterium, Lactobacillus and related genera

Minimal standards represent a collection of criteria that can be practically utilized for the description of new cultivable strains that represent novel genera and species in accordance with Recommendation 30b of the Bacteriological Code (1990 Revision). Due to the extraordinary importance of LAB and bifidobacteria in food fermentations, and their technological benefits for human and animal health, the publication of the Minimal Standards for the accurate taxonomic description and identification of species belonging to Bifidobacterium, Lactobacillus and related genera is a very important issue. These guidelines should be utilized consistently among all the researchers in order to minimize the risk of false allocation or duplications of new taxa. Modern taxonomic approach comprises phenotypic and genotypic characterization (polyphasic approach). Concerning genotypic characterization, in addition to DNA G+C content (mol%) data, the description should be based on DNA–DNA hybridization (DDH), 16S rRNA gene sequence similarities and at least two housekeeping gene (e.g. hsp60 and recA) sequence similarities. DDH might not be needed if the 16S rRNA gene sequence similarity to the closest known species is lower than 97 %. These guidelines are consistent with the most recently revisited standards of the microbial systematic community. The application of the above‐mentioned general criteria can provide a firm basis for the descriptions of novel genera and species. A general consideration could be that the minimal standards can provide a firm basis for the descriptions of novel genera and species, but due to rapid development of molecular techniques in taxonomy, updates should be envisaged from time to time