ИСТИНА

Sustainable usage of finite and non-renewable phosphorus (P) resources is a grave challenge to humanity. Shortage of P fertilizers threatens the food security. The P lost due in inefficient processing chain gives rise to eutrophication of water bodies. In view of this, potential environmental, social, and economic impact of currently non-sustainable usage of P is commensurate to that of oil and gas shortage. Single celled phototrophs including cyanobacteria and eukaryotic microalgae featuring so called “luxury uptake” of P constitute promising vehicle for by sequestering the lost P and returning it, in form of P-rich biomass, to the field. The reasons are (i) fast growth rate of these organism, (ii) capability of rapidly taking up P up to 4¬−7% of their cell dry weight, and (iii) gradual release of the accumulated P upon application of microalgal biomass to the soil in the from available to crop plants. Diazotrophic species of cyanobacteria are capable of fixing atmospheric nitrogen (N). On one hand, this process makes them less dependent on the availability of N in the medium so cyanobacteria can potentially recover P from waste streams with imbalanced N:P ratio. On the other hand, diazotrophy is a very energy-intensive process which can compete for ATP with the processes of P acquisition and storage in the cell. The successful biotechnological application of cyanobacteria to close the P loop is limited by insufficient understanding of C/N balance impact on and the molecular mechanisms of luxury P uptake. We report on the effect of diazotrophy on luxury P uptake and storage in the cell in a diazotroph strain Nostoc sp. PCC 7120 in comparison with a nearly-isogenic non-diazotroph strain Nostoc sp. PCC 7118. Although the P starvation and the fast phase of inorganic P (Pi) uptake were similar in both strains studied, induction of diazotrophy impared significantly the ability of PCC 7120 to accumulated inorganic polyphosphate (PolyP) in the cell. Since PolyP is a main P storage compound in the cell, the availability of N seems to of primary importance for efficient recovery of P from waste streams. Biotechnological implications of using diazotrophic and non-diazotrophic cyanobacterial strains for recovery of P from waste streams with different N/P balance are discussed. This studies of luxury P uptake in the cyanobacteria was supported by the Ministry of Science and Education of the Russian Federation (project 14.616.21.0080). The support of the polyphosphate accumulation studies by BioSC is greatly appreciated.