Structural variations in peptide toxins of Mycrocystis aeruginosa grown on different carbon sources

The nature of toxic peptides produced by Microcystis aeruginosa grown on low and high concentrations of different carbon sources (glucose, pyruvate, acetate and alpha-ketoglutarate) was studied. Fractionation and identification of the produced peptides were carried out using HPLC, mass spectrometry, and amino acid analyzer. At low concentrations of carbon sources, toxicity level was decreased, especially in the case of glucose and a-ketoglutarate treatments. This may be attributed to the disappearance of Microcystin-LR. On treating algae with high concentrations of carbon sources, the toxicity reached the minimum level as indicated by survival time. This may be due to the disappearance of the different toxin peptides other than Microcystin-RP. Mass spectroscopic results revealed m/z of the different produced peptide homologs of YA, RR and LR with basic molecular weights of: Mcyst-YA (m/z 959), Mcyst-RR (m/z 1037) and Mcyst-LR (m/z 994).