Classification and Taxonomy of Actinobacteria

The Pathogenic Role of Actinomyces spp. and Related Organisms in Genitourinary Infections: Discoveries in the New, Modern Diagnostic Era

“…The genera of Mobiluncus and Actinomyces form a monophyletic clade in a phylogenetic tree constructed based on RpoB, RpoC and DNA gyrase B protein sequences [17,18]. The existence of this clade is also strongly supported by a conserved signature indel, consisting of a three-amino-acid insertion in the isoleucine-tRNA synthetase found only in the species of the genera Actinomyces and Mobiluncus [16][17][18]. Actinomyces is one of six genera within the family Actinomycetaceae, and currently has 53 child taxa with validly published names, including synonyms [15][16][17][18][19].…”

“…Taxonomically, the genus Actinomyces belongs to the Actinomycetales order of the Actinobacteria phylum (characterized by high guanine-cytosine (G+C) content in their genome, e.g., 55%-68% in case of the Actinomyces genus (Figure 1)) [15]. The genomic evolution of the members of the family Actinomycetaceae is very dynamic, some studies observed that mutations or loss of genes in the species in the family contribute to changes in the microbial behavior and habitat preferences [16]. The genera of Mobiluncus and Actinomyces form a monophyletic clade in a phylogenetic tree constructed based on RpoB, RpoC and DNA gyrase B protein sequences [17,18].…”

“…The first deposited type strain of the Actinomyces species is A. bovis (as previously mentioned) [3,19]. There are three leading clusters by a phylogenetic tree based on 16S rRNA gene sequence comparisons, althought not all of them have been strengthened by the bootstrap analysis [16][17][18]. The majority of species belong to the cluster that includes A. bovis, while the other two clusters, which include Actinomyces neuii and Actinomyces hordeovulneris should be investigated further to determine if they warrant proposal as novel genera [16][17][18].…”

“…There are three leading clusters by a phylogenetic tree based on 16S rRNA gene sequence comparisons, althought not all of them have been strengthened by the bootstrap analysis [ 16 , 17 , 18 ]. The majority of species belong to the cluster that includes A. bovis , while the other two clusters, which include Actinomyces neuii and Actinomyces hordeovulneris should be investigated further to determine if they warrant proposal as novel genera [ 16 , 17 , 18 ]. The description of novel bacterial species was further facilitated by the newfound interest in the characterization of the human microbiome [ 20 ].…”

The Mycobacterial Cell Envelope: A Relict From the Past or the Result of Recent Evolution?

“…Several bacteria from the Corynebacteriales order, that includes M. tuberculosis , are studied for having an atypical structural characteristic: the presence of a so-called “mycomembrane” that, in an organizational sense, is believed to resemble the outer membrane of typical Gram-negative bacteria ( Zuber et al, 2008 ; Touchette and Seeliger, 2017 ; Figure 1 ). This mycomembrane is limited to members of the Corynebacteriales with some species-specific variation ( Goodfellow and Jones, 2015 ; Mohammadipanah and Dehhaghi, 2017 ). Besides the components common to other Gram-positive bacteria, Corynebacteriales also have a layer of arabinogalactan attached to the peptidoglycan layer and to the inner leaflet of the mycolic-acid containing mycomembrane.…”