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Journal of Bacteriology, April 2006, p. 2355-2363, Vol. 188, No. 7
0021-9193/06/$08.00+0 doi:10.1128/JB.188.7.2355-2363.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Pharmaceutical Sciences, College of Pharmacy,1 Markey Cancer Center and Center for Structural Biology,3 Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, Kentucky 405362
Received 13 October 2005/ Accepted 4 January 2006
We provide the first evidence for a link between polyamines and biofilm levels in Yersinia pestis, the causative agent of plague. Polyamine-deficient mutants of Y. pestis were generated with a single deletion in speA or speC and a double deletion mutant. The genes speA and speC code for the biosynthetic enzymes arginine decarboxylase and ornithine decarboxylase, respectively. The level of the polyamine putrescine compared to the parental speA+ speC+ strain (KIM6+) was depleted progressively, with the highest levels found in the Y. pestis
speC mutant (55% reduction), followed by the
speA mutant (95% reduction) and the
speA
speC mutant (>99% reduction). Spermidine, on the other hand, remained constant in the single mutants but was undetected in the double mutant. The growth rates of mutants with single deletions were not altered, while the
speA
speC mutant grew at 65% of the exponential growth rate of the speA+ speC+ strain. Biofilm levels were assayed by three independent measures: Congo red binding, crystal violet staining, and confocal laser scanning microscopy. The level of biofilm correlated to the level of putrescine as measured by high-performance liquid chromatography-mass spectrometry and as observed in a chemical complementation curve. Complementation of the
speA
speC mutant with speA showed nearly full recovery of biofilm to levels observed in the speA+ speC+ strain. Chemical complementation of the double mutant and recovery of the biofilm defect were only observed with the polyamine putrescine.
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