K. Flynn et al., CHANGES IN DINOFLAGELLATE INTRACELLULAR AMINO-ACIDS IN RESPONSE TO DIURNAL CHANGES IN LIGHT AND N-SUPPLY, Marine ecology. Progress series, 100(3), 1993, pp. 245-252
Seven species of dinoflagellates were examined with respect to their i
ntracellular amino acid (InAA) content under different conditions of N
-nutrition and light, and for release of dissolved free amino acids (D
FAA). Alexandrium spp. did not contain significant amounts of a neutra
l nonprotein amine present in all other phototrophic dinoflagellates t
ested but, in contrast, it always maintained high levels of glutamine
and of the ratio of intracellular glutamine/glutamate (Gln/Glu). Dinof
lagellates responded to a decreased availability of N with a fall in G
ln/Glu but, unlike other microalgae, arginine was always a significant
component of InAA. Refeeding of N-limited cultures with nitrate durin
g the dark phase of growth, simulating refeeding of a natural populati
on following a diurnal migration to the nutricline, resulted in an inc
reased Gln/Glu during the dark phase followed by a decline during the
light phase. N-refeeding of N-deprived cells led a rapid rise in the r
atio, except during N-refeeding of stationary phase Gymnodinium catena
tum (which were of abnormal shape and motility) when Glu rather than G
ln increased. The sensitivity of the analytical method would enable sa
mpling from natural dinoflagellate populations in order to assess thei
r physiological status; extracts from 200 to 2000 cells, depending on
cell size, are sufficient. A significant quantity of an unidentified a
mino acid accumulated in the growth media of Gymnodinium catenatum but
otherwise DFAA in dinoflagellate culture media were similar to that f
rom other microalgae.