Final answer:
Bacterial genomes primarily consist of unique sequences with minimal repetitive DNA. These genomes are compact, and their size varies based on the bacterium's dependency on its host for survival. Sequencing techniques have facilitated the study of these unique sequences and supercoiling allows the DNA to fit within the small bacterial cell.
Step-by-step explanation:
The majority of the DNA in a bacterial genome is comprised of unique sequences. Unlike eukaryotic genomes, which contain large portions of repetitive DNA like satellite DNA and transposons, bacterial genomes are mainly built from non-repetitive sequence DNA. These sequences include single-copy genes or operons that encode proteins, ribosomal RNAs, and transfer RNAs. Insights into bacterial genome complexity come from CoT curves and gene mapping studies, such as those carried out on E. coli, which indicate a lack of redundant DNA due to the small genome size.
Large-scale sequencing techniques, including shotgun sequencing, have been pivotal in understanding these genomes. Bacterial genomes can be extremely compact, with some being as small as 112,000 base pairs and others like E. coli measuring around 4.6 million base pairs. Bacteria often shed unnecessary genes when they can rely on a host organism for certain functions. In the bacterial cell, the DNA is densely packed through a process called supercoiling, aided by specific proteins and enzymes like DNA gyrase.