Provided herein is a genetically modified Y. pestis that includes three alterations compared to a control Y. pestis. Two alterations include decreased mRNA, decreased protein, or a combination thereof, encoded by a lpp coding region and encoded by a msbB coding region. The third alteration is selected from an alteration of an intergenic region between the coding regions ypo1119 and ypo1120, and decreased mRNA, decreased protein, or a combination thereof, encoded by a coding region selected from pla, ypol717, ypmt1.80c, rbsA (ypo2500), ypo0498, vasK (ypo3603), ypo3164, hxuB (ypo3248), ypo1616, ypo1119, ypo1120, and ail. Also provided are compositions that include the genetically modified Y. pestis, and methods of using the genetically modified Y. pestis. 展开▼
