title: Growth of calcium-blind mutants of Yersinia pestis at 37 degrees C in permissive Ca2+-deficient environments.
abstract: Cells of wild-type Yersinia pestis exhibit a low-calcium response (LCR) defined as bacteriostasis with expression of a pCD-encoded type III secretion system (T3SS) during cultivation at 37 degrees C without added Ca(2+) versus vegetative growth with downregulation of the T3SS with Ca(2+) (>or=2.5 mM). Bacteriostasis is known to reflect cumulative toxicity of Na(+), l-glutamic acid and culture pH; control of these variables enables full-scale growth ('rescue') in the absence of Ca(2+). Several T3SS regulatory proteins modulate the LCR, because their absence promotes a Ca(2+)-blind phenotype in which growth at 37 degrees C ceases and the T3SS is constitutive even with added Ca(2+). This study analysed the connection between the LCR and Ca(2+) by determining the response of selected Ca(2+)-blind mutants grown in Ca(2+)-deficient rescue media containing Na(+) plus l-glutamate (pH 5.5), where the T3SS is not expressed, l-glutamate alone (pH 6.5), where l-aspartate is fully catabolized, and Na(+) alone (pH 9.0), where the electrogenic sodium pump NADH : ubiquinone oxidoreductase becomes activated. All three conditions supported essentially full-scale Ca(2+)-independent growth at 37 degrees C of wild-type Y. pestis as well as lcrG and yopN mutants (possessing a complete but dysregulated T3SS), indicating that bacteriostasis reflects a Na(+)-dependent lesion in bioenergetics. In contrast, mutants lacking the negative regulator YopD or the YopD chaperone (LcrH) failed to grow in any rescue medium and are therefore truly temperature-sensitive. The Ca(2+)-blind yopD phenotype was fully suppressed in a Ca(2+)-independent background lacking the injectisome-associated inner-membrane component YscV but not peripheral YscK, suggesting that the core translocon energizes YopD.
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Fowler
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Christine R
authors.initials: CR
authors.lastname: Wulff
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Straley
authors.affiliation: Department of Microbiology, The University of Chicago, 920 E. 58th Street, Chicago, IL 60637, USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Brubaker
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D017353:Gene Deletion; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins / Q000378:metabolism; D055571:Secretory Pathway; D012964:Sodium / Q000378:metabolism; D013696:Temperature; D015010:Yersinia pestis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C088009:LcrG protein, Yersinia; D008565:Membrane Proteins; D018832:Molecular Chaperones; D052899:Pore Forming Cytotoxic Proteins; C118339:SycD protein, bacteria; C078910:YopD protein, Yersinia; C070015:YopN protein, Yersinia; D018698:Glutamic Acid; D012964:Sodium; D002118:Calcium