Morphological and biochemical changes of Microcystis aeruginosa PCC7806 subjected to dark and oxygen limitation

Abstract:

Abstract: ［Objective］ To explore the mechanism of cell death in Microcystis aeruginosa PCC 7806．［Method］According to the water environment of the later period of algal bloom，M． aeruginosa PCC 7806 was treat with dark and O2 limitation． We observed the morphological changes using transmission electron microscope (TEM) and detected the reactive oxygen species ( ROS) activity and Caspase3 activity in M． aeruginosa PCC7806 subjected to dark and O2 limitation． DNA status was also examined with the methods of Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) and agarose gel electrophoresis． ［Result］Massive algae cell died after 48 h treatment under dark and O2 limitation． During cell death process，we observed some changes of cell organelles including ribosomes and thylakoids disorganization，cytoplasmic vacuolation，nucleoplasm diffusion and plasmolysis in M． aeruginosa PCC7806 subjected to darkness and O2 limitation． Meanwhile，we found that increased ROS reactivity and capase 3 activity were related to the cell death process of M． aeruginosa． DNA breakage and fragmentation were proved by TUNEL staining and agarose gel electrophoresis during cell death process． ［Conclusion］All results showed that cell death with characteristics similar to eukaryotic programmed cell death could be induced in M． aeruginosa PCC 7806 after treatment with darkness and O2 limitation． Therefore，we suggested that the mechanism of cell death are conserved during evolution according to the characteristics of cell death shared between eukaryotes and Microcystis．

Key words:Keywords: Microcystis aeruginosa，cell death，caspase 3，reactive oxygen，DNA breakage