title: Analysis of the precursor rRNA fractions of rapidly growing mycobacteria: quantification by methods that include the use of a promoter (rrnA P1) as a novel standard.
abstract: Mycobacterial species are able to control rRNA production through variations in the number and strength of promoters controlling their rrn operons. Mycobacterium chelonae and M. fortuitum are members of the rapidly growing mycobacterial group. They carry a total of five promoters each, encoded, respectively, by one and two rrn operons per genome. Quantification of precursor rrn transcriptional products (pre-rrn) has allowed detection of different promoter usage during cell growth. Bacteria growing in several culture media with different nutrient contents were compared. Balanced to stationary phases were analyzed. Most promoters were found to be used at different levels depending on the stage of bacterial growth and the nutrient content of the culture medium. Some biological implications are discussed. Sequences of the several promoters showed motifs that could be correlated to their particular level of usage. A product corresponding to the first rrnA promoter in both species, namely, rrnA P1, was found to contribute at a low and near-constant level to pre-rRNA synthesis, regardless of the culture medium used and the stage of growth analyzed. This product was used as a standard to quantitate rRNA gene expression by real-time PCR when M. fortuitum infected macrophages. It was shown that this bacterium actively synthesizes rRNA during the course of infection and that one of its rrn operons is preferentially used under such conditions.
authors.affiliation: Departamento de Medicina Preventiva, Facultad de Medicina, Universidad Autonoma de Madrid, Arzobispo Morcillo s/n, 28029 Madrid, Spain.
authors.forename: María Del Carmen
authors.initials: Mdel C
authors.lastname: Menéndez
authors.forename: María José
authors.initials: MJ
authors.lastname: Rebollo
authors.forename: María Del Carmen
authors.initials: Mdel C
authors.lastname: Núñez
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cox
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: García
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003470:Culture Media / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D020459:Genes, rRNA; D006388:Hemagglutinins; D037102:Lectins; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D016926:Mycobacterium chelonae / Q000737:chemistry / Q000378:metabolism; D019907:Mycobacterium fortuitum / Q000737:chemistry / Q000378:metabolism; D009170:Nontuberculous Mycobacteria / Q000737:chemistry* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012322:RNA Precursors / Q000032:analysis* / Q000378:metabolism; D012329:RNA, Bacterial / Q000032:analysis / Q000378:metabolism; D012335:RNA, Ribosomal / Q000032:analysis* / Q000378:metabolism; D012407:rRNA Operon
chemical_list: D003470:Culture Media; D006388:Hemagglutinins; D037102:Lectins; D012322:RNA Precursors; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; C104578:heparin-binding hemagglutinin