title: The organization of two rRNA (rrn) operons of the slow-growing pathogen Mycobacterium celatum provides key insights into mycobacterial evolution.
abstract: The slow-growing Mycobacterium celatum is known to have two different 16S rRNA gene sequences. This study confirms the presence of two rrn operons and describes their organization. One operon (rrnA) was found to be located downstream from murA and the other (rrnB) was found downstream from tyrS. The promoter regions were sequenced, and also the intergenic transcribed spacer (ITS1 and ITS2) regions separating the 16S rRNA, 23S rRNA and 5S rRNA gene coding regions. Analysis of the RNA fraction revealed that rrnA is regulated by two (P1 and PCL1) promoters and rrnB is regulated by one (P1). These data show that the two rrn operons of M. celatum are organized in the same way as the two rrn operons of classical fast-growing mycobacteria. This information was incorporated into a phylogenetic analysis of the genus based on both 16S rRNA gene sequences and (where possible) the number of rrn operons per genome. The results suggest that the ancestral Mycobacterium possessed two (rrnA and rrnB) operons per genome and that subsequently, on two separate occasions, an operon (rrnB) was lost, leading to two clusters of species having a single operon (rrnA); one cluster includes the classical pathogens and the other includes Mycobacterium abscessus and Mycobacterium chelonae.
authors.affiliation: Departamento de Microbiologia, ENCB-IPN, Prolongacion de Carpio y Plan de Ayala s/n Del. Miguel Hidalgo, Mexico DF.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Stadthagen-Gomez
authors.forename: A Cecilia
authors.initials: AC
authors.lastname: Helguera-Repetto
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Cerna-Cortes
authors.forename: Richard A
authors.initials: RA
authors.lastname: Goldstein
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cox
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Gonzalez-y-Merchand
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification; D001483:Base Sequence; D021901:DNA, Intergenic / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000145:classification / Q000235:genetics* / Q000254:growth & development; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D024363:Transcription Initiation Site; D012407:rRNA Operon
chemical_list: D001426:Bacterial Proteins; D021901:DNA, Intergenic; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012335:RNA, Ribosomal