Flow cytometry and metabolomics revealed different inorganic phosphorus response mechanisms of Chlorella pyrenoidosa

Inorganic phosphorus (IP) is a vital nutrient essential for the growth and metabolism of microorganisms. However, the physiological and biochemical responses of microalgae to different IP forms and their potential mechanisms remain unclear. In this study, the effects of three IP forms, including orthophosphate (orthoP), pyrophosphate (pyroP), and polyphosphate (polyP), on the growth, physiological status and metabolomics of Chlorella pyrenoidosa (C. pyrenoidosa) were investigated. Analysis of intracellular and extracellular phosphorus contents revealed that the assimilation efficiency of pyroP was 17.1 % lower than that of orthoP forms, indicating lower bioavailability. Flow cytometry quantitatively showed that pyroP induced hypertrophy in C. pyrenoidosa cells and reduced the proportion of living cells. PolyP was found to promote protein synthesis, and the proportion of protein was 4.1 % higher than that of orthoP group. A metabolomics analysis further confirmed that different IP forms affected the intracellular biochemical composition and phosphorus transport pathways by regulating intracellular amino acid and nucleotide synthesis. This study provides a theoretical foundation for the microalgae cultivation by utilizing different forms phosphorus, and has significance for the recovery of phosphorus in wastewater.