Effects of nitrogen and phosphorus starvation on nucleic acid and protein content of Heterocapsa sp

Changes in the protein, RNA and DNA content related to nitrogen (N) and phosphorus (P) starvation were studied in the marine dinoflagellate Heterocapsa sp. grown in batch cultures. In both cases of nutrient starvation, metabolic adaptations affected protein and RNA pools, while the DNA content per cell remained approximately constant. N starvation led to a parallel de crease in protein and RNA concentration which caused the protein/RNA ratios to remain constant. A dramatic decrease in the RNA content characterized the P-starved cultures, although protein synthesis continued. The ribosomal RNA content was lower than expected given the continuation of protein synthesis. It is suggested that protein/RNA ratios could be used as an indicator of P starvation, while protein/chlorophyll ratios would characterize N starvation.