it is possible that E. coli experiences high-magnesium concentration under some environmental conditions. In such conditions, H-NS can switch from its filament inducing form to the bridge inducing form that contributes to DNA condensation and organization. Fis Factor for Inversion Stimulation (Fis) is a sequence specific DNA binding protein that binds to specific DNA sequences containing a 15-bp symmetric motif. Like IHF, Fis induces DNA bending at cognate sites. The ability to bend DNA is apparent in the structure of Fis homodimer. A Fis homodimer possesses two helix-turn-helix (HTH) motifs, one from each monomer. An HTH motif typically recognizes the DNA major groove. However, the distance between the DNA recognition helices of the two HTH motifs in the Fis homodimer is 25 Å, that is ~ 8 Å shorter than the pitch of a canonical B-DNA, indicating that the protein must bend or twist DNA to bind stably. Consistently, the crystal structure of Fis-DNA complexes shows that the distance between the recognition helices remains unchanged whereas DNA curves in the range of 60-75 degree. There are 1464 Fis binding regions distributed across the E. coli genome and a binding motif, identified computationally, matches with the known 15-bp motif. Specific binding of Fis at such sites would induce bends in DNA, thus contribute to DNA condensation by reducing persistence length of DNA. Furthermore, many Fis binding sites occur in tandem such as those in the stable RNA promoters, e.g., P1 promoter of rRNA operon rrnB. The coherent bending by Fis at the tandem sites is likely to create a DNA micro-loop that can further contribute to DNA condensation. Besides high-affinity specific binding to cognate sites, Fis can bind to a random DNA sequence. The non-specific DNA binding is significant because Fis is as abundant as HU in the growth phase. Therefore, most of Fis molecules are expected to bind DNA in a non-sequence specific manner. Magnetic tweezers experiments show that this non-specific binding of Fis can contribute to DNA condensation and organization. Fis causes mild condensation of a single DNA molecule at <1 mM, but induces substantial folding through the formation of DNA loops of an average size of ~800 bp at >1 mM. The loops in magnetic tweezers experiments are distinct from the micro-loops created by coherent DNA bending at cognate sites, as they require the formation of high-density DNA-protein complexes achieved by sequence-independent binding. Although, occurrence of such loops