Some chemical and biological properties of culture filtrate ofNostochopsis lobatus

The blue-green algaNostochopsis lobatus released amino acids (glycine, serine, arginine and glutamic acid), sugars (glucose, fructose and sucrose), organic acids (oxaloacetic acid and oxalic acid) and protein in the culture medium. The quantity of extracellular amino acids and protein increased with age of culture from 30 to 120 d. All culture filtrates ofN. lobatus were highly toxic to spore formation and germination ofWestiellopsis prolifica and growth and conjugation ofSpirogyra decimina, while old-age culture filtrates inhibited total chlorophyll, heterocyst and akinete formation in the same alga and total chlorophyll and zoospore formation inChaetophora attenuata. The toxicity ofN. lobatus culture filtrate persists following high temperature treatment and at extremes of pH.