title: Analysis of expression profile of mce operon genes (mce1, mce2, mce3 operon) in different Mycobacterium tuberculosis isolates at different growth phases.
abstract: OBJECTIVE
  Mycobacterium tuberculosis (M. tuberculosis) has four homologous mammalian cell entry (mce) operons (mce1-4) that encode exported proteins and have a possible role in the virulence mechanism of this pathogen. The expression of mce operon is considered to be complex and not completely understood. Although expression of mce operon at different in vitro growth phases has been studied earlier, its expression in different M. tuberculosis isolates under different growth phases is not yet studied. The present preliminary study was conducted on a limited number of isolates to know the trend of expression pattern of mce operon genes in different M. tuberculosis isolates under different growth stages.
  
  
  METHODS
  In this study, we monitored the transcriptional profile of selected mce operon genes (mce1A, mce1D, mce2A, mce2D, mce3A, mce3C) in different M.tuberculosis isolates (MDR1, MDR2, and sensitive isolate) at early exponential and stationary phases using real-time quantitative PCR.
  
  
  RESULTS
  The expression ratio of all selected mce operon genes in all M. tuberculosis isolates was reduced at the initial phase and increased substantially at a later phase of growth. Higher expression of mce1 operon genes was found in all M. tuberculosis isolates as compared to other mce operon genes (mce2 and mce3 operons) at stationary growth phase.
  
  
  CONCLUSIONS
  the higher expression of mce operon genes at stationary phase (as compared to early exponential phase) suggested growth phase dependent expression of mce operon genes. This indicated that the mce operon genes might have a role in M. tuberculosis survival and adaptation on the onset of adverse condition like stationary phase. Identification of differentially expressed genes will add to our understanding of the bacilli involved in adaptation to different growth conditions.
authors.affiliation: Department of Microbiology & Molecular Biology, National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Agra, India.
authors.forename: Pratibha
authors.initials: P
authors.lastname: Singh
authors.affiliation: Department of Microbiology & Molecular Biology, National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Agra; Former Secretary, Department of Health Research and Director-General, ICMR, Ministry of Health & Family Welfare, Government of India, New Delhi, India.
authors.forename: V M
authors.initials: VM
authors.lastname: Katoch
authors.affiliation: Department of Immunology, National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Agra, India.
authors.forename: K K
authors.initials: KK
authors.lastname: Mohanty
authors.affiliation: Department of Microbiology & Molecular Biology, National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Agra, India.
authors.forename: Devendra Singh
authors.initials: DS
authors.lastname: Chauhan
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis* / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D009876:Operon / Q000235:genetics; D014376:Tuberculosis / Q000235:genetics / Q000382:microbiology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C510663:Mce3A protein, Mycobacterium tuberculosis; C473802:mammalian cell entry protein Mce1A, Mycobacterium tuberculosis; C443482:mce2 protein, Mycobacterium tuberculosis