FIG 5 .

Cellular responses to SCV and transcriptional suppressor mutations. SCV-inducing mutations in the hemin or menadione biosynthesis pathways abolish cellular respiration. As a phenotypic compensation, genes involved in the arginine deiminase (ADI) pathway are upregulated, increasing the production of ATP from arginine to support growth. SCV suppressor mutations in srrAB cause constitutive activation of the SrrAB two-component system, which leads to increased expression of genes involved in peptide transport and in the fermentation of serine and threonine to produce ATP and NAD⁺.