Polyphosphate: A Multifunctional Metabolite in Cyanobacteria and Algae

Abstract

Polyphosphate (polyP), a polymer of orthophosphate (PO 4 3-) of varying lengths, has been identified in all kingdoms of life. It can serve as a source of chemical bond energy (phosphoanhydride bond) that may have been used by biological systems prior to the evolution of ATP. Intracellular polyP is mainly stored as granules in specific vacuoles called acidocalcisomes, and its synthesis and accumulation appear to impact a myriad of cellular functions. It serves as a reservoir for inorganic PO 4 3and an energy source for fueling cellular metabolism, participates in maintaining adenylate and metal cation homeostasis, functions as a scaffold for sequestering cations, exhibits chaperone function, covalently binds to proteins to modify their activity, and enables normal acclimation of cells to stress conditions. PolyP also appears to have a role in symbiotic and parasitic associations, and in higher eukaryotes, low polyP levels seem to impact cancerous proliferation, apoptosis, procoagulant and proinflammatory responses and cause defects in TOR signaling. In this review, we discuss the metabolism, storage, and function of polyP in photosynthetic microbes, which mostly includes research on green algae and cyanobacteria. We focus on factors that impact polyP synthesis, specific enzymes required for its synthesis and degradation, sequestration of polyP in acidocalcisomes, its role in cellular energetics, acclimation processes, and metal homeostasis, and then transition to its potential applications for bioremediation and medical purposes.

Lipidome Remodeling and Autophagic Respose in the Arachidonic-Acid-Rich Microalga Lobosphaera incisa Under Nitrogen and Phosphorous Deprivation

“…VTC4 putatively encodes a polyP polymerase subunit of the vacuolar transporter chaperone complex (VTC). VTC4 is involved in polyP synthesis in acidocalcisomes, and microautophagy in yeast (Livermore et al, 2016), but its function has not yet been studied genetically in photosynthetic organisms (Sanz-Luque et al, 2020). VTC4 showed a different expression pattern under P and N deprivation, attaining maximal levels after 2 and 5 days, respectively.…”

Phosphorus Feast and Famine in Cyanobacteria: Is Luxury Uptake of the Nutrient Just a Consequence of Acclimation to Its Shortage?

“…Most of the inorganic phosphate (P i ) taken up via LPU is stored in the cell in the form of osmotically inert polyphosphate (PolyP) granules [ 13 ], accommodating P sufficient for up to 20 cell divisions [ 14 ] and playing a plethora of other biological roles [ 1 , 4 , 15 ], including a potential role of energy storage [ 16 ]. In general, PolyP is accumulated when the P i influx into the cell is larger than its current metabolic demand and there is enough surplus energy (ATP).…”

Biomineralization of Sr by the Cyanobacterium Pseudanabaena catenata Under Alkaline Conditions

“…Polyphosphate bodies are made up of many orthophosphate residues that are linked by phosphoanhydride bonds to form linear polymers, and can be found in many organisms, and are particularly prevalent in photosynthetic microorganisms (Achbergerová and Nahálka, 2011;Albi and Serrano, 2016;Sanz-Luque et al, 2020). Previous studies have shown that polyphosphate bodies can have a variety of metals associated with them, with the most commonly studied metals including Cd, Pb, and Ca (Baxter and Jensen, 1980;Jensen et al, 1982;Albi and Serrano, 2016).…”