Final answer:
Tension in the bacterial supercoiled genome is relaxed by topoisomerases, specifically DNA gyrase, which transiently breaks and rejoins the phosphate backbone of the DNA, relieving the tension ahead of the replication fork.
Step-by-step explanation:
Tension in the bacterial supercoiled genome is relaxed by topoisomerases, specifically DNA gyrase (topoisomerase II) in bacteria. This enzyme is responsible for counteracting the supercoiling that naturally occurs as the DNA helix unwinds for replication. DNA supercoiling can either be under-wound or over-wound from its normal relaxed state, and if not managed, it could cause the phosphodiester bonds within the DNA to rupture, leading to fragmentation.
Topoisomerase works by transiently breaking and then rejoining the phosphate backbone of the DNA. This action relieves the supercoiled tension, which is crucial for many cellular processes such as replication, transcription, and chromosomal segregation. By doing so ahead of the replication fork, it allows the DNA strands to be separated and for replication machinery to access the genetic code properly.
The remarkable ability to manage DNA tension avoids potential damage to the genome and ensures the orderly transmission of genetic information. Given the size of bacterial genomes like that of E. coli, which consists of approximately 4.6 million base pairs, the role of topoisomerases like DNA gyrase is essential for fitting DNA within the confines of the bacterial cell while maintaining its functionality.