Question

Which one of the following \(\sigma\) (sigma) factors is responsible for the transcriptional regulation of nitrogen assimilation?

• A. \(\sigma 70\)
• B. \(\sigma 54\)
• C. \(\sigma 28\)
• D. \(\sigma 24\)

Hint:

\(\sigma 54\) is also called nitrogen sigma factor because it regulates genes involved in nitrogen fixation and assimilation.

Answer 1

The Correct Option is B

Step 1: Role of sigma factors.
A sigma factor steers RNA polymerase to the right promoters. Different sigmas switch on different gene sets.

Step 2: Match the famous ones.
Sigma 70 runs everyday housekeeping genes. Sigma 28 turns on flagella and motility. Sigma 24 handles envelope and heat stress.

Step 3: Pin down nitrogen control.
Sigma 54, also written sigma N, is the one tied to nitrogen metabolism, including nitrogen assimilation and fixation.

Step 4: Answer.
So the right factor is sigma 54. \[ \boxed{\sigma 54} \]