Changes in motility and induction of enzymatic activity by nitrogen and phosphate deficiency in benthic Halamphora luciae (Bacillariophyceae) from Argentina

Abstract

Cells of Halamphora luciae were isolated from the mudflat of the Bahía Blanca estuary. Unialgal axenic cultures were grown in f/2 with limiting concentrations of N or P and in f/2 medium deprived of one or both macronutrients. On the one hand, limited macronutrient supply did not affect growth rate, but final cell yield was lower than in the complete medium. On the other hand, N or P deprivation reduced growth rates as well as final cell yield in the stationary phase. P deficiency enhanced the secretion of soluble extracellular polymeric substances (EPS), the percentage and speed of gliding cells, as well as the activity of alkaline phosphatase, especially after a previous prolonged P starvation. Regarding the morphology of the frustules, P deprivation reduced areola size but did not alter cell biovolume. N deficiency had a deleterious effect on the motility of the cells, and reduced the secretion of soluble EPS and cell biovolume. After incubation in N-deprived media for 10 days, cells exhibited enhanced protease activity.