title: Identification of a novel gene product that promotes survival of Mycobacterium smegmatis in macrophages.
abstract: BACKGROUND
  Bacteria of the suborder Corynebacterineae include significant human pathogens such as Mycobacterium tuberculosis and M. leprae. Drug resistance in mycobacteria is increasingly common making identification of new antimicrobials a priority. Mycobacteria replicate intracellularly, most commonly within the phagosomes of macrophages, and bacterial proteins essential for intracellular survival and persistence are particularly attractive targets for intervention with new generations of anti-mycobacterial drugs.
  
  
  RESULTS
  We have identified a novel gene that, when inactivated, leads to accelerated death of M. smegmatis within a macrophage cell line in the first eight hours following infection. Complementation of the mutant with an intact copy of the gene restored survival to near wild type levels. Gene disruption did not affect growth compared to wild type M. smegmatis in axenic culture or in the presence of low pH or reactive oxygen intermediates, suggesting the growth defect is not related to increased susceptibility to these stresses. The disrupted gene, MSMEG_5817, is conserved in all mycobacteria for which genome sequence information is available, and designated Rv0807 in M. tuberculosis. Although homology searches suggest that MSMEG_5817 is similar to the serine:pyruvate aminotransferase of Brevibacterium linens suggesting a possible role in glyoxylate metabolism, enzymatic assays comparing activity in wild type and mutant strains demonstrated no differences in the capacity to metabolize glyoxylate.
  
  
  CONCLUSIONS
  MSMEG_5817 is a previously uncharacterized gene that facilitates intracellular survival of mycobacteria. Interference with the function of MSMEG_5817 may provide a novel therapeutic approach for control of mycobacterial pathogens by assisting the host immune system in clearance of persistent intracellular bacteria.
authors.affiliation: Department of Microbiology, Monash University, Clayton, Victoria, Australia.
authors.forename: Assunta
authors.initials: A
authors.lastname: Pelosi
authors.forename: Danielle
authors.initials: D
authors.lastname: Smith
authors.forename: Rajini
authors.initials: R
authors.lastname: Brammananth
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Topolska
authors.forename: Helen
authors.initials: H
authors.lastname: Billman-Jacobe
authors.forename: Phillip
authors.initials: P
authors.lastname: Nagley
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crellin
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D004251:DNA Transposable Elements / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D015321:Gene Rearrangement / Q000235:genetics; D018390:Gene Targeting; D005798:Genes, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D006801:Humans; D042541:Intracellular Space / Q000382:microbiology; D008264:Macrophages / Q000166:cytology / Q000382:microbiology*; D051379:Mice; D050296:Microbial Viability / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D009165:Mycobacterium Infections, Nontuberculous / Q000382:microbiology; D020102:Mycobacterium smegmatis / Q000166:cytology* / Q000235:genetics* / Q000254:growth & development; D016328:NF-kappa B / Q000378:metabolism; D010587:Phagocytosis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D021901:DNA, Intergenic; D016328:NF-kappa B; D012333:RNA, Messenger