The enzyme creates or removes supercoiling in the duplex DNA by creating transitory breaks in the DNA strands. The supercoiling is a fundamental property of the DNA and the chromatin structures. The DNA gets organized in loop domains in the E. coli bacteria. The bacterial chromosomal DNA gets a thousandfold compact structure forming looped domains. In E. coli, each domain consists of a 40Kb loop coiled negatively. An E. coli genome consists of approximately a hundred domains. The nucleoid isolation studies revealed that the E. coli DNA does not freely rotate once a break gets introduced into the DNA. Introduction of breaks affects the rotation of the double helix. Hence, it also affects the supercoiling property of the DNA. There arises a loss of DNA supercoiling due to the breaks. It happens mainly because the DNA is not alone, but attached to proteins. The structure of an E. coli nucleoid seems to be very interesting. The supercoiled DNA loops radiate from the central protein core. The protein component consists of DNA gyrase and DNA topoisomerase-I. They help in maintaining the supercoiled state of the DNA. The E. coli consists of total 40 to 50 supercoiled DNA loops. Each loop consists of 100 Kb supercoiled DNA. It is the amount of DNA that unwinds after introducing a break.