RNA-seq gene expression data for Synechococcus sp. WH8102 under continuous high, mid, and low phosphorus treatments in laboratory EFB experiments in 2025

While P availability strongly affected growth rates, single-cell C:N:P stoichiometry and the expression of P-stress genes, polyP:TPP increased with decreasing growth rate, reproducing the pattern observed in oligotrophic marine environments. This shift was not driven by polyP accumulation; instead, cellular polyP concentrations remained relatively stable across growth rates (ANOVA, p = 0.16), while other intracellular P pools—including RNA, free Pi, ATP and phospholipids—were preferentially depleted with decreasing P availability (ranging from 2.6- to 11.8-fold, respectively), increasing the relative contribution of polyP to total cellular P. Gene expression analysis revealed little transcription differences between polyP-metabolism associated genes.

These results indicate that cellular polyP content is maintained independently of growth rate under steady-state conditions, suggesting that P deficiency responses observed in oligotrophic environments and various microorganisms in batch culture reflect slow-growing physiology (differential pool lability over selective polyP retention), with consequences for interpreting particulate P stoichiometry and export.