C. Leboulanger et al., PHOTORESPIRATION IN CONTINUOUS-CULTURE OF DUNALIELLA-TERTIOLECTA (CHLOROPHYTA) - RELATIONSHIPS BETWEEN SERINE, GLYCINE, AND EXTRACELLULAR GLYCOLATE, Journal of phycology, 34(4), 1998, pp. 651-654
The concentrations of extracellular glycolate and intracellular free p
ools of serine and glycine were monitored in nitrogen-limited continuo
us cultures of Dunaliella tertiolecta (Butcher) UTEX LB999, grown at t
wo different irradiances on a light:dark cycle. Under steady-state con
ditions, this microalga excreted into the medium a large amount of gly
colate during the light phase, up to 100 nmol.(10(6) cells)(-1) for a
cell concentration of around 1.5 10(8) cells.L-1, but glycolate disapp
eared from the dissolved phase in the dark. Cells grown at 70 and thos
e grown at 430 mu mol photons m(-2).s(-1) differed in maximal glycolat
e concentration, intracellular serine and glycine concentrations, and
serine:glycine ratio. Reversal of these photon flux densities to which
the cultures were exposed caused rapid modification of the extracellu
lar glycolate and intracellular serine and glycine pools. These result
s suggest that photorespiratory metabolism in D. tertiolecta could be
approximately quantified by measuring the changes in dissolved glycola
te and intracellular serine and glycine concentrations, extending prev
ious results from cultured phytoplankton and suggesting methods for fi
eld studies.