Influence of Na(+), dicarboxylic amino acids, and pH in modulating the low-calcium response of Yersinia pestis.
The virulence of yersiniae is promoted in part by shared approximately 70-kb plasmids (pCD in Yersinia pestis and pYV in enteropathogenic Yersinia pseudotuberculosis and Yersinia enterocolitica) that mediate a low-calcium response. This phenotype is characterized at 37 degrees C by either bacteriostasis in Ca(2+)-deficient medium with expression of pCD/pYV-encoded virulence effectors (Yops and LcrV) or vegetative growth and repression of Yops and LcrV with > or =2.5 mM Ca(2+) (Lcr(+)). Regulation of Yops and LcrV is well defined but little is known about bacteriostasis other than that Na(+) plus l-glutamate promotes prompt restriction of Y. pestis. As shown here, l-aspartate substituted for l-glutamate in this context but only Na(+) exacerbated the nutritional requirement for Ca(2+). Bacteriostasis of Y. pestis (but not enteropathogenic yersiniae) was abrupt in Ca(2+)-deficient medium at neutral to slightly alkaline pH (7.0 to 8.0), although increasing the pH to 8.5 or 9.0, especially with added Na(+) (but not l-glutamate), facilitated full-scale growth. Added l-glutamate (but not Na(+)) favored Ca(2+)-independent growth at acidic pH (5.0 to 6.5). Yops and LcrV were produced in Ca(2+)-deficient media at pH 6.5 to 9.0 regardless of the presence of added Na(+) or l-glutamate, although their expression at alkaline pH was minimal. Resting Ca(2+)-starved Lcr(+) cells of Y. pestis supplied with l-glutamate first excreted and then destroyed l-aspartate. These findings indicate that expression of Yops and LcrV is necessary but not sufficient for bacteriostasis of Ca(2+)-starved yersiniae and suggest that abrupt restriction of Y. pestis requires Na(+) and the known absence of aspartate ammonia-lyase in this species.
Brubaker
Robert R
RR
Department of Microbiology and Molecular Genetics, 2209 Biophysical Medical Sciences Building, Michigan State University, East Lansing, MI 48824, USA. brubake3@msu.edu
D000600:Amino Acids, Dicarboxylic / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors; D015008:Yersinia enterocolitica / Q000378:metabolism; D015010:Yersinia pestis / Q000378:metabolism*; D015011:Yersinia pseudotuberculosis / Q000378:metabolism
D000600:Amino Acids, Dicarboxylic; D001224:Aspartic Acid; D018698:Glutamic Acid; D012964:Sodium; D002118:Calcium