The two-component PhoR-PhoP system controls both primary metabolism and secondary metabolite biosynthesis in <i>Streptomyces lividans</i>

TLDR

Inorganic phosphate strongly represses secondary metabolite production, and the PhoR‑PhoP two‑component system of *Streptomyces lividans*—where PhoR is a membrane‑bound sensor and PhoP a DNA‑binding regulator—has been cloned and characterized. Deletion of phoR‑phoP abolishes growth and alkaline phosphatase production under low‑phosphate conditions while simultaneously up‑regulating actinorhodin and undecylprodigiosin synthesis; complementation restores normal growth, phosphatase activity, and phosphate‑dependent repression of secondary metabolites, demonstrating that PhoR‑PhoP controls both phoA expression and secondary metabolite biosynthesis.

Abstract

The biosynthesis of most secondary metabolites in different bacteria is strongly depressed by inorganic phosphate. The two-component phoR-phoP system of Streptomyces lividans has been cloned and characterized. PhoR showed all of the characteristics of the membrane-bound sensor proteins, whereas PhoP is a member of the DNA-binding OmpR family. Deletion mutants lacking phoP or phoR-phoP , were unable to grow in minimal medium at low phosphate concentration (10 μM). Growth was fully restored by complementation with the phoR-phoP genes. Both S. lividans Δ phoP and Δ phoR-phoP deletion mutants were unable to synthesize extracellular alkaline phosphatase (AP) as shown by immunodetection with anti-AP antibodies and by enzymatic analysis, suggesting that the PhoR-PhoP system is required for expression of the AP gene ( phoA ). Synthesis of AP was restored by complementation of the deletion mutants with phoR-phoP . The biosynthesis of two secondary metabolites, actinorhodin and undecylprodigiosin, was significantly increased in both solid and liquid medium in the Δ phoP or Δ phoR-phoP deletion mutants. Negative phosphate control of both secondary metabolites was restored by complementation with the phoR-phoP cluster. These results prove that expression of both phoA and genes implicated in the biosynthesis of secondary metabolites in S. lividans is regulated by a mechanism involving the two-component PhoR-PhoP system.