Requirement of integration host factor (IHF) for growth of Escherichia coli deficient in HU protein

Escherichia coli mutants deficient in histone-like protein, HU, and integration host factor (IHF) were constructed and their growth characteristics were examined. Mutants deficient in both HU and IHF grew slowly and were filamentous at both 30 degrees C and 37 degrees C. These mutants scarcely grew in LB broth at 42 degrees C. They formed minute colonies on LB plates at 42 degrees C and no colonies at 46 degrees C, indicating temperature-sensitive (ts) growth. On the contrary, mutants deficient in either HU or IHF were not ts for growth. These results indicate that IHF compensates for the absence of HU and permits normal cell growth; this suggests functional similarity between HU and IHF.