Final answer:
RNA polymerase identifies the start site in bacteria with the σ factor and terminates transcription via Rho-dependent or Rho-independent mechanisms involving the rho factor or terminator stem, respectively.
Step-by-step explanation:
In bacteria, RNA polymerase recognizes the transcription start site with the help of the σ (sigma) factor, which binds to specific consensus sequences in the promoter region, commonly known as the '-35' region and the 'Pribnow box.' This helps to position the RNA polymerase correctly to begin transcription.
Transcription termination in bacteria can occur via two mechanisms: Rho-dependent termination, where a protein called rho factor unwinds the RNA-DNA hybrid, and Rho-independent termination, which involves the formation of a terminator stem - a stable RNA secondary structure that leads to the stalling and release of the RNA polymerase from the DNA template.
Both mechanisms ensure that transcription only occurs for the required length of DNA and that the RNA polymerase dissociates afterwards, allowing the RNA transcript to be processed and used for protein synthesis.