title: Amino Acid Catabolism inStaphylococcus aureusand the Function of Carbon Catabolite Repression.
abstract: Staphylococcus aureusmust rapidly adapt to a variety of carbon and nitrogen sources during invasion of a host. Within a staphylococcal abscess, preferred carbon sources such as glucose are limiting, suggesting thatS. aureussurvives through the catabolism of secondary carbon sources.S. aureusencodes pathways to catabolize multiple amino acids, including those that generate pyruvate, 2-oxoglutarate, and oxaloacetate. To assess amino acid catabolism,S. aureusJE2 and mutants were grown in complete defined medium containing 18 amino acids but lacking glucose (CDM). A mutation in thegudBgene, coding for glutamate dehydrogenase, which generates 2-oxoglutarate from glutamate, significantly reduced growth in CDM, suggesting that glutamate and those amino acids generating glutamate, particularly proline, serve as the major carbon source in this medium. Nuclear magnetic resonance (NMR) studies confirmed this supposition. Furthermore, a mutation in theackAgene, coding for acetate kinase, also abrogated growth of JE2 in CDM, suggesting that ATP production from pyruvate-producing amino acids is also critical for growth. In addition, although a functional respiratory chain was absolutely required for growth, the oxygen consumption rate and intracellular ATP concentration were significantly lower during growth in CDM than during growth in glucose-containing media. Finally, transcriptional analyses demonstrated that expression levels of genes coding for the enzymes that synthesize glutamate from proline, arginine, and histidine are repressed by CcpA and carbon catabolite repression. These data show that pathways important for glutamate catabolism or ATP generation via Pta/AckA are important for growth in niches where glucose is not abundant, such as abscesses within skin and soft tissue infections.IMPORTANCES. aureusis a significant cause of both morbidity and mortality worldwide. This bacterium causes infections in a wide variety of organ systems, the most common being skin and soft tissue. Within a staphylococcal abscess, levels of glucose, a preferred carbon source, are limited due to the host immune response. Therefore,S. aureusmust utilize other available carbon sources such as amino acids or peptides to proliferate. Our results show that glutamate and amino acids that serve as substrates for glutamate synthesis, particularly proline, function as major carbon sources during growth, whereas other amino acids that generate pyruvate are important for ATP synthesis via substrate-level phosphorylation in the Pta-AckA pathway. Our data support a model whereby certain amino acid catabolic pathways, and acquisition of those particular amino acids, are crucial for growth in niches where glucose is not abundant.
authors.affiliation: University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, Nebraska, USA.
authors.forename: Cortney R
authors.initials: CR
authors.lastname: Halsey
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
authors.forename: Shulei
authors.initials: S
authors.lastname: Lei
authors.affiliation: University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, Nebraska, USA.
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Wax
authors.affiliation: University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, Nebraska, USA.
authors.forename: Mckenzie K
authors.initials: MK
authors.lastname: Lehman
authors.affiliation: Department of Biology, University of Nebraska at Kearney, Kearney, Nebraska, USA.
authors.forename: Austin S
authors.initials: AS
authors.lastname: Nuxoll
authors.affiliation: University of Nebraska Medical Center, Department of Biochemistry and Molecular Biology, Omaha, Nebraska, USA.
authors.forename: Laurey
authors.initials: L
authors.lastname: Steinke
authors.affiliation: University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, Nebraska, USA.
authors.forename: Marat
authors.initials: M
authors.lastname: Sadykov
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, USA rpowers3@unl.edu pfey@unmc.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Powers
authors.affiliation: University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, Nebraska, USA rpowers3@unl.edu pfey@unmc.edu.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fey
mesh_terms: D000038:Abscess / Q000382:microbiology; D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics*; D002244:Carbon / Q000378:metabolism*; D057465:Catabolite Repression; D020869:Gene Expression Profiling; D005947:Glucose / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism*; D009154:Mutation; D013211:Staphylococcus aureus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D018698:Glutamic Acid; D002244:Carbon; D000255:Adenosine Triphosphate; D005969:Glutamate Dehydrogenase; D005947:Glucose