The DNA relaxation-dependent OFF-to-ON biasing of the type 1 fimbrial genetic switch requires the Fis nucleoid-associated protein.

The structural genes expressing type 1 fimbriae in alternate between expressed (phase ON) and non-expressed (phase OFF) states due to inversion of the 314 bp genetic switch. The FimB tyrosine integrase inverts by site-specific recombination, alternately connecting and disconnecting the operon encoding the fimbrial subunit protein and its associated secretion and adhesin factors, to and from its transcriptional promoter within . Site-specific recombination by the FimB recombinase becomes biased towards phase ON as DNA supercoiling is relaxed, a condition that occurs when bacteria approach the stationary phase of the growth cycle.

Reciprocally rewiring and repositioning the Integration Host Factor (IHF) subunit genes in serovar Typhimurium: impacts on physiology and virulence.

The Integration Host Factor (IHF) is a heterodimeric nucleoid-associated protein that plays roles in bacterial nucleoid architecture and genome-wide gene regulation. The and genes encode the subunits and are located 350 kbp apart, in the Right replichore of the chromosome. IHF is composed of one IhfA and one IhfB subunit.

Network Rewiring: Physiological Consequences of Reciprocally Exchanging the Physical Locations and Growth-Phase-Dependent Expression Patterns of the and Genes.

The Fis nucleoid-associated protein controls the expression of a large and diverse regulon of genes in Gram-negative bacteria. Fis production is normally maximal in bacteria during the early exponential phase of batch culture growth, becoming almost undetectable by the onset of stationary phase. We tested the effect on the Fis regulatory network in of moving the complete gene from its usual location near the origin of chromosomal replication to the position normally occupied by the gene in the right macrodomain of the chromosome, and vice versa, creating the ene echange (GX) strain.