title: A novel taxonomic marker that discriminates between morphologically complex actinomycetes.
abstract: In the era when large whole genome bacterial datasets are generated routinely, rapid and accurate molecular systematics is becoming increasingly important. However, 16S ribosomal RNA sequencing does not always offer sufficient resolution to discriminate between closely related genera. The SsgA-like proteins are developmental regulatory proteins in sporulating actinomycetes, whereby SsgB actively recruits FtsZ during sporulation-specific cell division. Here, we present a novel method to classify actinomycetes, based on the extraordinary way the SsgA and SsgB proteins are conserved. The almost complete conservation of the SsgB amino acid (aa) sequence between members of the same genus and its high divergence between even closely related genera provides high-quality data for the classification of morphologically complex actinomycetes. Our analysis validates Kitasatospora as a sister genus to Streptomyces in the family Streptomycetaceae and suggests that Micromonospora, Salinispora and Verrucosispora may represent different clades of the same genus. It is also apparent that the aa sequence of SsgA is an accurate determinant for the ability of streptomycetes to produce submerged spores, dividing the phylogenetic tree of streptomycetes into liquid-culture sporulation and no liquid-culture sporulation branches. A new phylogenetic tree of industrially relevant actinomycetes is presented and compared with that based on 16S rRNA sequences.
authors.affiliation: Molecular Biotechnology, Institute of Biology, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Girard
authors.forename: Bjørn A
authors.initials: BA
authors.lastname: Traag
authors.forename: Vartul
authors.initials: V
authors.lastname: Sangal
authors.forename: Nadine
authors.initials: N
authors.lastname: Mascini
authors.forename: Paul A
authors.initials: PA
authors.lastname: Hoskisson
authors.forename: Michael
authors.initials: M
authors.lastname: Goodfellow
authors.forename: Gilles P
authors.initials: GP
authors.lastname: van Wezel
mesh_terms: D039903:Actinobacteria / Q000145:classification* / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D007218:Industrial Microbiology; D008847:Micromonospora / Q000145:classification / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013171:Spores, Bacterial / Q000502:physiology; D013306:Streptomycetaceae / Q000145:classification / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; C414488:ssgA protein, bacterial
keywords: Streptomyces; cell division; genome sequencing; systematics