MICROCYSTIN CHANGES AND PROTEOMIC RESPONSES OF MICROCYSTIS AERUGINOSA EXPOSED TO CADMIUM DURING COLONY FORMATION.

Microcystis occurs as colonies in natural waters and always disaggregates into unicellular cells in the laboratory. Cadmium (Cd) could stimulate Microcystis colony formation in the laboratory. To elucidate the mechanism involved in cadmium-induced colony formation of Microcystis, microcystin (MC) changes and proteomic responses in M. aeruginosa treated with seven concentrations of Cd (0, 0.0125, 0.0250, 0.0500, 0.1000, 0.2000 and 0.4000 mg/L) for 40 h were studied. The results showed that seven concentrations of Cd except 0.4000 mg/L Cd could significantly induce colony formation (P < 0.05), and the Cd-induced colony-stimulating effects were accompanied with the increased intracellular MC-RR production. A total of 1170 proteins, including seven MC biosynthesis-related enzymes and seven polysaccharide biosynthesis-related enzymes, were identified using 2D-LC-MS/MS combined with isobaric tags for relative and absolute quantitation (iTRAQ). 0.4000 mg/L Cd could downregulate all the identified enzymes involved in MC and polysaccharide biosynthesis while most of these enzymes were upregulated during Cd-induced colony formation. Cd might stimulate Microcystis colony formation via increasing the biosynthesis of MC and polysaccharide. [ABSTRACT FROM AUTHOR]