Proposal for a New Hierarchic Classification System, Actinobacteria classis nov.

TLDR

Traditional actinomycete genus boundaries largely follow 16S rRNA phylogeny, yet higher taxonomic levels have historically ignored phylogenetic clustering, rendering broad families and higher taxa vague due to the rich chemical, morphological, and physiological diversity among closely related genera. The study proposes a new hierarchical classification system for actinomycetes that clusters phylogenetically adjacent genera into families, suborders, orders, subclasses, and a class based solely on 16S rRNA/rDNA phylogeny and signature nucleotides. The system delineates taxa using only 16S rDNA/rRNA sequence‑based phylogenetic clustering and taxon‑specific 16S rDNA RNA signature nucleotides, rather than chemotaxonomic, morphological, or physiological traits.

Abstract

A new hierarchic classification structure for the taxa between the taxonomic levels of genus and class is Proposed for the actinomycete line of descent as defined by analysis of small subunit (16S) rRNA and genes coding for this molecule (rDNA). While the traditional circumscription of a genus of the actinomycete subphylum is by and large in accord with the 16S rRNA/rDNA-based phylogenetic clustering of these organisms. most of the higher taxa proposed in the past do not take into account the phylogenetic clustering of genera. The rich chemical, morphological and physiological diversity of phylogenetically closely related genera makes the description of families and higher taxa so broad that they become meaningless for the description of the enclosed taxa. Here we present a classification system in which phylogenetically neighboring taxa at the genus level are clustered into families, suborders, orders, subclasses, and a class irrespective of those phenotypec characteristics on which the delineation of taxa has been based in the past. Rather than being based on a listing of a wide array of chemotaxonomic, morphological, and physiological properties, the delineation is based solely on 16S rDNA/rRNA sequence-based phylogenetic clustering and the presence of taxon-specific 16S rDNA RNA signature nucleotides.