Which sigma factor is also called housekeeping sigma factor?
Sigma70, encoded by rpoD, is the primary housekeeping sigma factor of Escherichia coli and most Gram-negative bacteria active during exponential growth. It directs RNA polymerase to the majority of promoters driving essential genes for central metabolism, ribosome synthesis, and cell envelope production, recognizing consensus -35 TTGACA and -10 TATAAT sequences. Housekeeping activity ensures continuous expression of vegetative functions. Under stress or developmental change, alternative sigma factors such as sigma32 for heat shock, sigma38 for general stress, sigma28 for flagella, and sigma54
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 9: Prokaryotic transcription and housekeeping sigma70 function