Correct option is B
Explanation-
Sigma factors are proteins that help RNA polymerase recognize specific sets of genes for transcription.
E. coli has multiple sigma factors, each responding to different environmental conditions.
σ⁷⁰ (Sigma 70) - Housekeeping sigma factor, responsible for regular gene transcription during normal growth.
σ³² (Sigma 32) - Heat shock sigma factor, upregulates genes needed for heat shock response / thermal stress adaptation.
σ⁵⁴ (Sigma 54) - Nitrogen starvation response.
σ⁴⁵ (Sigma 45) - Less commonly referenced, but related to stationary phase / starvation responses (similar to σ^S or σ^38).
E. coli responds to thermal stress (heat shock) by activating heat shock proteins (HSPs). The transcription of heat shock genes (like dnaK, groEL, groES) is directly regulated by sigma factor σ³². A mutation in σ³² (rpoH gene) would impair this transcriptional response, and E. coli would fail to adapt to thermal stress.
Correct Answer: Option b - σ³² (Sigma 32)
