Transposon-induced mutants of Listeria monocytogenes incapable of growth at low temperature (4 degrees C).

Transposon mutagenesis was used to pursue the molecular basis of cold resistance in Listeria and its possible involvement in pathogenesis. We have generated transposon-induced mutants of Listeria monocytogenes which were unable to grow at 4 degrees C but grew at 8 degrees C, 22 degrees C and 37 degrees C. The transposon was localized in the same 1.8-kb EcoRI fragment in two independently derived mutants. Mutants which carried single transposon insertions had normal hemolytic activity, motility and invasion of cultured fibroblasts. These results indicate that in L. monocytogenes cold sensitivity can be single transposon insertions and that loss of cold resistance may not interfere with other phenotypes, including invasion in a cell culture model.