Abstract <p>Bacterial chromosomes are tightly packed in the cells due to interactions with specific nucleoid-associated proteins. Among them, the IHF protein draws attention due to its presumed influence on intracellular crystallization processes, leading to bacterial resistance to drugs. The crystal structure of the IHF heterodimer is known only in complex with a short DNA fragment, whereas the structure of this heterodimer in solution has not yet been established due to its tendency to further oligomerize. In this study, the structural characteristics of the individual IHF heterodimer were determined for the first time under nearly physiological conditions by small-angle X-ray scattering. This structure was compared with the high-resolution crystal structure. These results are required to address pressing issues related to bacterial resistance.</p>