Impact of Neurotransmitters on the Photosynthetic Pigment Content of the Green Microalga Haematococcus lacustris (Strains IPPAS H-239 and BM-1)

Abstract The effects of the neurotransmitters serotonin (5-НТ), histamine, dopamine (DA), norepinephrine (NE), and acetylcholine (ACh) at concentrations of 0.1–10 μM on the contents of chlorophylls ( а and b ) and carotenoids in strains IPPAS B-239 and BM-1 of the microalga Haematococcus lacustris are considered. In the strain H. lacustris BM-1, all tested neurotransmitters except serotonin were found to stimulate carotenoid formation with an increase in the carotenoid content in the cells. The stimulatory effect was quite significant with acetylcholine and especially histamine and was manifested less with dopamine and norepinephrine. Carotenoid formation by strain IPPAS H-239 was only stimulated by acetylcholine and, to a lesser extent, by norepinephrine. The other neurotransmitters inhibited carotenoid formation. The total chlorophyll a and b content increased in the presence of all tested neurotransmitters except serotonin in strain BM-1. As for strain IPPAS H-239, its chlorophyll content was increased by acetylcholine and norepinephrine, whereas histamine and serotonin lowered the chlorophyll content. It is suggested that the tested neurotransmitters influence the vegetative cell—palmelloid cell—encysted cell transition, fixing it at the intermediate brown palmelloid stage characterized by significant chlorophyll and carotenoid contents.