A systems-level insight into PHB-driven metabolic adaptation orchestrated by the PHB-binding transcriptional regulator AniA (PhaR)

Abstract

Poly(3-hydroxybutyrate) (PHB) is a carbon and energy storage polymer typically associated with bacterial survival under nutrient-limited conditions. Its accumulation reflects the cellular metabolic balance, and the transcriptional regulator PhaR has been shown to bind PHB and control the expression of genes involved in its metabolism. At the same time, PhaR has been implicated in broader regulatory roles affecting global gene expression, although the connection between this function and its ability to sense PHB has remained unresolved. In this study, we used the model legume symbiont Sinorhizobium meliloti to bridge this gap. We demonstrated that PhaR modulates global gene expression in response to the metabolic state signaled by PHB accumulation. Our findings highlight PHB not only as a storage compound, but also as a key integrator of metabolic status that links nutrient availability to coordinated transcriptional responses.