Effects of <i>Yersinia pestis</i> Fra-Operon Carriage on the Cellular Morphologic Features of the Recipient <i>Yersinia pseudotuberculosis</i> Strain

Cellular morphologic variations of Yersinia pseudotuberculosis strain 164/84 were assessed depending on the cultivation temperature and the plague agent's fra-operon carriage by these cells. Notably slower population growth of the two isogenic variants of strain 164/84 (fra+ and fra-) was observed at the cultivation temperatures of 4 to 6 °C as compared with those at 26-28 °C and 36-38 °C. Only late growth stages at the temperatures of 36 to 38 °C brought about significant differences between the fra+ and fra- cell variants expressed in the occurrence of relatively bigger cells in the population of the capsule forming Y. pseudotuberculosis variant