title: Peptidoglycan synthesis in Mycobacterium tuberculosis is organized into networks with varying drug susceptibility.
abstract: Peptidoglycan (PG), a complex polymer composed of saccharide chains cross-linked by short peptides, is a critical component of the bacterial cell wall. PG synthesis has been extensively studied in model organisms but remains poorly understood in mycobacteria, a genus that includes the important human pathogen Mycobacterium tuberculosis (Mtb). The principle PG synthetic enzymes have similar and, at times, overlapping functions. To determine how these are functionally organized, we carried out whole-genome transposon mutagenesis screens in Mtb strains deleted for ponA1, ponA2, and ldtB, major PG synthetic enzymes. We identified distinct factors required to sustain bacterial growth in the absence of each of these enzymes. We find that even the homologs PonA1 and PonA2 have unique sets of genetic interactions, suggesting there are distinct PG synthesis pathways in Mtb. Either PonA1 or PonA2 is required for growth of Mtb, but both genetically interact with LdtB, which has its own distinct genetic network. We further provide evidence that each interaction network is differentially susceptible to antibiotics. Thus, Mtb uses alternative pathways to produce PG, each with its own biochemical characteristics and vulnerabilities.
authors.affiliation: Department of Immunology and Infectious Disease, Harvard T. H. Chan School of Public Health, Boston, MA 02115;
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Kieser
authors.affiliation: Department of Immunology and Infectious Disease, Harvard T. H. Chan School of Public Health, Boston, MA 02115;
authors.forename: Catherine
authors.initials: C
authors.lastname: Baranowski
authors.affiliation: Division of Infectious Diseases, Brigham & Women's Hospital, Boston, MA 02115;
authors.forename: Michael C
authors.initials: MC
authors.lastname: Chao
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester MA 01655;
authors.forename: Jarukit E
authors.initials: JE
authors.lastname: Long
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester MA 01655; Howard Hughes Medical Institute, Chevy Chase, MD 20815;
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Sassetti
authors.affiliation: Division of Infectious Diseases, Brigham & Women's Hospital, Boston, MA 02115; Howard Hughes Medical Institute, Chevy Chase, MD 20815; Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115;
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Waldor
authors.affiliation: Department of Biochemistry and Biophysics and Department of Chemistry, Texas A&M University, College Station, TX 77843;
authors.forename: James C
authors.initials: JC
authors.lastname: Sacchettini
authors.affiliation: Department of Computer Science, Texas A&M University, College Station, TX 77843.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Ioerger
authors.affiliation: Department of Immunology and Infectious Disease, Harvard T. H. Chan School of Public Health, Boston, MA 02115; Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; erubin@hsph.harvard.edu.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Rubin
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010457:Peptidoglycan / Q000096:biosynthesis*
chemical_list: D000995:Antitubercular Agents; D010457:Peptidoglycan
keywords: Mycobacterium tuberculosis; cell wall; genetic interaction; peptidoglycan; transposon sequencing