Fig 9. Working model for the role of SrrAB in modulating the transcription of genes utilized in H₂O₂ resistance and dioxygen respiration.

SrrAB modulates gene transcription in response to cellular respiratory flux [36]. We propose that increased culture aeration leads to increased respiratory flux during post-exponential growth, which results in altered kinase activity of SrrB and variation in the cellular pool of SrrA~P. An altered SrrA~P pool results in increased expression of genes under the SrrAB regulon that are utilized for H₂O₂ resistance and dioxygen respiration. The resultant physiological changes allow for cellular homeostasis by protecting macromolecules against H₂O₂ toxicity that arise during dioxygen respiration.