title: A Nonsense Mutation in Mycobacterium marinum That Is Suppressible by a Novel Mechanism.
abstract: Mycobacterial pathogens use the ESAT-6 system 1 (Esx-1) exporter to promote virulence. Previously, we used gene disruption and complementation to conclude that the MMAR_0039 gene in Mycobacterium marinum is required to promote Esx-1 export. Here we applied molecular genetics, proteomics, and whole-genome sequencing to demonstrate that the MMAR_0039 gene is not required for Esx-1 secretion or virulence. These findings suggest that we initially observed an indirect mechanism of genetic complementation. We identified a spontaneous nonsense mutation in a known Esx-1-associated gene which causes a loss of Esx-1 activity. We show that the Esx-1 function was restored by nonsense suppression. Moreover, we identified a polar mutation in the ppsC gene which reduced cellular impermeability but did not impact cytotoxicity in macrophages. Our studies reveal insight into Esx-1 export, nonsense suppression, and cell envelope lipid biogenesis.
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Emily A
authors: EA
authors: Williams
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Felix
authors: F
authors: Mba Medie
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Rachel E
authors: RE
authors: Bosserman
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors: Benjamin K
authors: BK
authors: Johnson
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Cristal
authors: C
authors: Reyna
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Micah J
authors: MJ
authors: Ferrell
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA.
authors: Matthew M
authors: MM
authors: Champion
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors: Robert B
authors: RB
authors: Abramovitch
authors: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA pchampio@nd.edu.
authors: Patricia A
authors: PA
authors: Champion
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D018389:Codon, Nonsense; D015964:Gene Expression Regulation, Bacterial; D009165:Mycobacterium Infections, Nontuberculous / Q000382:microbiology; D019910:Mycobacterium marinum / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D010641:Phenotype; D021381:Protein Transport; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D018389:Codon, Nonsense
keywords: Esx-1; PDIM; complementation; mycobacteria; nonsense suppression; spontaneous mutation