Isolation of thermosensitive mutants of Yersinia enterocolitica by transposon insertion

During bacterial infection, pathogens are exposed to a variety of stimuli, e.g., sudden temperature increase on entering mammalian host or oxidative stress associated with exposure to phagocytes. Yersinia enterocolitica, which is a facultative intracellular bacteria, responds to macrophage phagocytosis by the production of a set of stress proteins; which are also induced by heat shock (Yamamoto et al., 1994, Microbiol. Immunol. 38, 295-300). To examine the role of bacterial stress proteins in the adaptation to environmental changes encountered during infectious processes, we have isolated stress-sensitive mutants from Y. enterocolitica in which mini-Tn10 transposon insertions allow bacterial growth at 28 degrees C but prevent growth at an elevated temperature, 39 degrees C. Eight independent insertions were obtained and preliminarily characterized by Southern blot hybridization and morphological analysis.