Phosphate Homeostasis in Conditions of Phosphate Proficiency and Limitation in the Wild Type and the phoP Mutant of Streptomyces lividans

Abstract

Phosphate, as a constituent of the high energy molecules, ATP/GTP and polyphosphate, plays a crucial role in most of the metabolic processes of living organisms. Therefore, the adaptation to low Pi availability is a major challenge for bacteria. In Streptomyces, this adaptation is tightly controlled by the two component PhoR/PhoP system. In this study, the free intracellular Pi, ATP, ADP and polyP content of the wild type and the phoP mutant strain of S. lividans TK24 were analyzed at discrete time points throughout growth in Pi replete and limited media. PolyP length and content was shown to be directly related to the Pi content of the growth medium. In Pi repletion, ATP and high molecular weight (HMW) polyP contents were higher in the phoP mutant than in the WT strain. This supports the recently proposed repressive effect of PhoP on oxidative phosphorylation. High oxidative phosphorylation activity might also have a direct or indirect positive impact on HMW polyP synthesis. In Pi sufficiency as in Pi limitation, the degradation of these polymers was shown to be clearly delayed in the phoP mutant, indicating PhoP dependent expression of the enzymes involved in this degradation. The efficient storage of Pi as polyphosphate and/or its inefficient degradation in Pi in the phoP mutant resulted in low levels of free Pi and ATP that are likely to be, at least in part, responsible for the very poor growth of this mutant in Pi limitation. Furthermore, short polyP was shown to be present outside the cell, tightly bound to the mycelium via electrostatic interactions involving divalent cations. Less short polyP was found to be associated with the mycelium of the phoP mutant than with that of the WT strain, indicating that generation and externalization of these short polyP molecules was directly or indirectly dependent on PhoP.

The master regulator PhoP coordinates phosphate and nitrogen metabolism, respiration, cell differentiation and antibiotic biosynthesis: comparison in Streptomyces coelicolor and Streptomyces avermitilis

“…23 This protein has three enzyme activities: polyphosphate synthase, polyphosphate hydrolase and phospholipase. 24,25 Oxidative phosphorylation and nitrate respiration genes Another important class of genes regulated by inorganic phosphate, whose expression is mediated by PhoP, are the oxidative phosphorylation genes, including several cytocrome C and B oxidase complexes, NADH dehydrogenase complex, succinate dehydrogenase and genes for nitrate respiration ( Table 1). Several of these genes are also regulated by the redox response regulator Rex.…”

Expression of genes of the Pho regulon is altered in Streptomyces coelicolor

“…This allowed a much better understanding of the metabolic differences between the two strains and revealed the unexpected significantly lower abundance, in SC compared to SL, of the sensor kinase PhoR and the response regulator PhoP. This two-component system is known to control positively and negatively, respectively, phosphate (Pi) [18][19][20] and nitrogen (N) assimilation [21][22][23] . The low abundance of PhoR/PhoP in SC resulted in the tuning down of its regulatory role and thus in a lower abundance of proteins involved in Pi scavenging and uptake in SC than in SL, leading to a severe Pi limitation in SC.…”

Structural and biochemical analysis of a phosin fromStreptomyces chartreusisreveals a combined polyphosphate‐ and metal‐binding fold

“…As soon as falling P i concentrations render uptake via low‐affinity transport systems inadequate, the sensory kinase PhoR autophosphorylates and transfers its phosphoryl group to the response regulator PhoP . This transcription factor represses a range of metabolic pathways while activating the expression of proteins involved in re‐establishing P i homeostasis and the scavenging of P i from external sources. The latter include secreted phosphatases as well as low‐ and high‐affinity phosphate transport systems, PitH2 and PstSCAB .…”