Towards a taxonomy of Bacteria and Archaea based on interactive and cumulative data repositories
Taxonomy in the second decade of the 21st century is benefiting from technological advances in molecular microbiology, especially those related to genomics. Gene and genome databases are significantly increasing due to intense research activities in the field of molecular ecology and genomics. Taxa, and especially species, are tailored by means of the recognition of a phylogenetic, genomic and phenotypic coherence that reveal their uniqueness in the classification schema. Phylogenetic coherence is mainly revealed by means of 16S rRNA gene analyses for which curated databases such as EzTaxon and LTP provide a valuable tool for tree reconstruction to taxonomy users. On the other hand, in silico full or partial genomic sequence comparisons are called on to substitute cumbersome techniques such as DNA–DNA hybridization (DDH) to genomically circumscribe species. DDH similarity values around 70% would be equivalent to ANI values of 96%. Finally, finding an exclusive phenotypic property for the taxa to be classified is of paramount relevance to producing an operative and predictive classification system. The current methods used for taxonomic classification require significant laboratory experimentation, and generally will not produce interactive databases. The new high-throughput metabolomic technologies, such as ICR-FT and MALDI-TOF mass spectrometry methods, open the door to the construction of metabolic databases for taxonomic purposes. It is to be foreseen that, in the future, taxonomists will benefit significantly from public databases speeding up the classification process. However, serious effort will be needed to harmonize them and to prevent inaccurate material.