Integration host factor (IHF) is a heterodimeric histone-like DNA-binding protein that participates in many cellular functions. Many systems and global regulators of acid resistance (AR) under strongly acidic conditions have been reported, but the role of IHF has not been examined. In the present study, we report that IHF is necessary for the induction of AR in Escherichia coli. At acidic pH, a a dagger ihfAa dagger ifhB-mutant strain was found to have significantly depressed levels of transcription of the arginine decarboxylase gene (adiA) and of translation of the lysine/cadaverine antiporter gene (cadB), when compared with wild-type strain. Thus, IHF induces the arginine- and lysine-dependent AR. These results indicate that in E. coli, by combined transcriptional and translational controls of gene expression, IHF activates expression of a specific set of genes required for survival at extremely acidic pH.