Study of defense mechanism of microalgae Haematococcus pluvialis infected by Paraphysoderma sedebokerensis

In the present study, the first early physiological responses of the green micro algae Haematococcus pluvialis during infection by chytrid Paraphysoderma sedebokerensis was studied. To this end, the palmeloid form of Haematococcus pluvialis was cultivated for two days in three media including the medium infected with chytrid (chyt) and the culture of chytrid infected (IBS) and uncontaminated (HBS) cells. Then, the activity of antioxidant enzymes, extracellular peroxide, and free intracellular enzymes were determined by UV/Vis spectrophotometry and HPLC techniques. The activity of superoxide dismutase, catalase, and peroxidase in the chytrid infected cells after 24, 24, and 48 h was 2.3, 6.7, and 2.6 times higher those of control. These values for the cells cultivated with the infected media after 12, 12, and 36 h was found to be 2.1, 2.5, and 2.6 times higher than control. The extracellular peroxide content in the algae cultivated with the contaminated media was nearly constant and about 4 fold of the other specimens; while those of chytrid infected cells was slightly increased from 1.3 to 1.8 μM during 48 h cultivation. Amino acids histidine, alanine, asparagine, aspatic acid, arginine, and methionine were of the highest and the phenylalanine and tryptophan were of the lowest content. These results can be attributed to the cells defense response to chytrid infection thorough enhancement of peroxide content and activation of antioxidative pathways.