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Infect Immun. 1974 June; 9(6): 1105-1113
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Effect of Ca²⁺ on Morphology and Division of Yersinia pestis

^a Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan 48823

ABSTRACT

Wild-type cells of Yersinia pestis are known to exhibit a nutritional requirement for physiological levels of Ca²⁺ (2.5 mM) at 37 but not 26 C. Upon shift of Ca²⁺-deficient cultures from 26 (permissive condition) to 37 C (restrictive condition), bacterial mass quadrupled as the organisms doubled in number and then became elongated to about twice their normal size. As shown in thin sections, the resulting static cells contained axial filaments which differed from the typical irregularly lobate nucleoids of normal yersiniae grown under the permissive condition. Following prolonged cultivation under the restrictive condition (12 h), the organisms generally exhibited apparent degenerative changes, including separation or infolding of the cell wall and cytoplasmic membrane, degeneration of deoxyribonucleic acid, and appearance of vacuoles within the cytoplasm. At this time, the cells were unable to reinitiate cell division at 37 C upon addition of Ca²⁺ but divided in partial synchrony after return to 26 C. This observation indicated that, at 37 C, continuous exposure to Ca²⁺ is necessary for yersiniae to maintain normal morphology and the ability to divide.

¹ Present address: Department of Microbiology University of Tennessee Medical Units, Memphis, Tenn. 38103.

² Present address: Department of Bacteriology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, N.C. 27514.