Fig. 9. Differential gene expression and nitrogen fixation rate at P-VI of the Synechococcus and heterotrophic bacteria coculture system.

(A) GSEA of the significantly up-regulated genes at P-VI [P = 0.05, number of permutation (nPerm) = 10,000]. Heatmap representation of expression levels for differentially expressed transcripts (log₂ fold change, adjusted P value of 0.05) related to (B) inorganic phosphorus mineralization and (C) the nitrogen cycle processes. (D) Changes in δ¹⁵N incorporation in PN and DN in the coculture system over 48 hours. CC-I and CC-II represent cocultures I and II with the addition of the ¹⁵N tracer. The accompanying dashed line represents the control set (without the addition of the ¹⁵N tracer) for CC-I and CC-II, respectively. (E) Nitrogen fixation rates (after subtracting their respective controls) within the PN and DN pools of CC-I and CC-II upon incubation for 48 hours. Each data point is an average of two replicates, with error bars showing the standard error of the mean. CC-I, coculture I; CC-II, coculture II.