Figure 1

Global metabolic profiling of supernatants of P. falciparum-infected erythrocytes. (a) Volcano plot depicting fold change (X-axis) in 141 metabolites between normal RBCs and P. falciparum-infected erythrocytes (iRBCs) with their statistical significance indicated by the Y-axis. The scatter points on the left and right of zero in the fold change (FC) axis represent down-regulated and up-regulated metabolites, respectively. Circles towards the top in the Y-axis represent metabolites that have been affected with statistical significance (P- value < 0.05; separated by a grey line) while the circles towards the lower half of the Y-axis represent metabolites with P-value > 0.05. Each circle is representative of a metabolite. Red circles indicate metabolites with a FC > 2 and P-value < 0.05. Green circles indicate metabolites with a FC < 2 and P-value < 0.05. Yellow circles indicate metabolites that are affected with a P-value < 0.05, but not significant with respect to FC threshold. Colored black circles indicate metabolites that are statistically insignificant (P- value > 0.05) and have insignificant FC. Open black circles indicate metabolites that have a fold change < or >2, but are not statistically significant (P-value < 0.05). The data presented correspond to the statistical analysis of n = 5 independent biological replicates and 4 technical replicates. (b) Pathway impact analysis plot showing metabolic pathways affected across time and infection with statistical significance. The radius of the circle represents the number of metabolites identified in each pathway. The color gradient from white to red is representative of the cumulative statistical significance of the pathway and the individual pathway impact on the overall metabolic change observed. (c) Pie chart representing the percentage of metabolites involved in different processes that changed between the normal group and the infected group in Plasmodium culture supernatant. Most of the metabolites that were up/down regulated in the infected group belonged to the lipid (34%) and amino acid metabolic pathways (24%). Redox metabolites, xenobiotics and carbohydrate metabolism also contributed a significant percentage of metabolites that exhibited a change in the two groups. (d) Heat map representation of changes in metabolite levels measured in culture supernatants of P. falciparum-infected RBCs at ring, trophozoite and schizont stages. Green rectangles indicate a down regulation in the metabolite level and red rectangles indicate an increase in metabolite level. Most metabolites show an increase in their levels as P. falciparum intra-erythrocyte development progresses to the schizont stage. (e) The schematic representation of a global metabolic map showing the 141 metabolites identified from P. falciparum-infected RBC culture supernatants. Colours in the map represent the different pathways in which these metabolites are involved. In each of these pathways, the highlighted metabolites have been identified in the current study.