Temperature dependent alteration in bacterial protein composition

When different strains of $\text{Escherichia coli}$ or $\text{Salmonella}$ are grown at 30° or at 42° and their proteins are compared using SDS-polyacrylamide gel electrophoresis, differences are observed in the protein composition of the cells. In particular, one major difference is in a protein of molecular weight of approximately 58,000, which is made at 42° but not at 30°.