The influence of microamounts of organic substances other than vitamins on the growth of some red algae in axenic culture

Several red algae in axenic culture decline in artificial seawater after a period of cultivation. Nemalion helminthoides rapidly loses its brown-red colour and grows with longer and thinner threads. Extracts of contaminated red algae, or nutrient medium in which they have grown, as well as fresh seawater from the Fucus-Ascophyllum zone, enhance growth and restore the pigmentation of the cells. Addition of 40 mg Bacto-Casamino acids per litre of nutrient medium had the same effect. After fractional precipitation with ethyl alcohol and separation on a Sephadex column the activity was localised to a peptide fraction. Results from chromatography point to effects from a low molecular weight substance active alone or coupled to a peptide.