length (persistence length). This model was supported by observations that removal of the cell wall or inhibition of cell wall synthesis increased the radius of the cell and resulted in a concomitant increase in the helical radius and a decrease in the helical pitch in the nucleoid. Nucleoid-membrane connections An expansion force due to DNA-membrane connections appears to function in opposition to condensation forces to maintain an optimal condensation level of the nucleoid. Cell-fractionation and electron microscopy studies first indicated the possibility of DNA-membrane connections. There are now several known examples of DNA-membrane connections. Transertion is a mechanism of concurrent transcription, translation, and insertion of nascent membrane proteins that forms transient DNA-membrane contacts. Transertion of two membrane proteins LacY and TetA has been demonstrated to cause the repositioning of chromosomal loci toward the membrane. Another mechanism of nucleoid-membrane connections is through a direct contact between membrane-anchored transcription regulators and their target sites in the chromosome. One example of such as transcription regulator in E. coli is CadC. CadC contains a periplasmic sensory domain and a cytoplasmic DNA binding domain. Sensing of an acidic environment by its periplasmic sensory domain stimulates DNA binding activity of CadC, which then activates transcription of its target genes. The membrane-localization of genes regulated by a membrane-anchored transcription regulator is yet to be demonstrated. Nonetheless, activation of target genes in the chromosome by these regulators is expected to result in a nucleoid-membrane contact albeit it would be a dynamic contact. Besides these examples, the chromosome is also specifically anchored to the cell membrane through protein-protein interaction between DNA-bound proteins, e.g., SlmA and MatP, and the divisome. Since membrane-protein encoding genes are distributed throughout the genome, dynamic DNA-membrane contacts through transertion can act as a nucleoid expansion force. This expansion force would function in opposition to condensation forces to maintain an optimal condensation level. The formation of highly condensed nucleoids upon the exposure of E. coli cells to chloramphenicol, which blocks translation, provides support for the expansion force of transient DNA-membrane contacts formed through transertion. The round shape of overly-condensed nucleoids after chloramphenicol treatment also suggests a role for transertion-mediated DNA-membrane contacts in defining the ellipsoid shape of the nucleoid. Visualization The nucleoid can be clearly visualized on an electron micrograph at very high magnification, where, although its appearance may differ, it is clearly visible against the cytosol. Sometimes even strands of what is thought to be