Which statement about bacterial transcription initiation is true?

• A. Eukaryotes require sigma factors and promoter elements such as the -35 and -10 regions
• B. Bacteria use sigma factors to recognize promoter elements such as the -35 and -10 regions
• C. Transcription initiation is identical in bacteria and eukaryotes
• D. RNA polymerase in bacteria does not require promoters

Answer: (B)

Bacterial transcription initiation depends on the RNA polymerase holoenzyme being guided to promoter DNA by a sigma factor. The sigma factor recognizes specific promoter sequences, notably the -35 and -10 regions, which are located upstream of the transcription start site. Once the sigma factor binds these elements, it helps the polymerase melt the DNA and align the active center to begin RNA synthesis at the +1 site. This orchestration by sigma factors is what makes the statement true.

Eukaryotes do not use sigma factors for promoter recognition; they rely on a set of general transcription factors and different promoter elements, so the first option is not accurate for bacteria. Transcription initiation is not identical between bacteria and eukaryotes due to the distinct factors and promoter architectures involved. And RNA polymerase in bacteria absolutely requires promoter DNA (with the help of sigma) to initiate transcription, so the last option is incorrect.