AXENIC CULTURE STUDIES OF A NEW MARINE PHYCOMYCETE POSSESSING AN UNUSUAL TYPE OF ASEXUAL REPRODUCTION

Abstract

Investigations of a nonfilamentous fungus (Schizochytrium aggregatum gen. et sp. nov.) reveal that it proliferates zoosporangia by successive bipartitioning of the thallus. Thus, its vegetative reproduction differs from that of other fungi, but resembles that of some possibly primitive chlorosphaeracean algae. Organism development is described from growth on natural substrates and synthetic media. Inoculation experiments involving diverse algae and phanerogam materials suggest that S. aggregatum is largely a saprophyte of vascular plant detritus in the littoral zone—a conclusion consonant with the results of a survey of its apparent distribution in coastal waters. This obligately marine organism requires 2.5‐3.0% NaCl for optimal growth and does not develop in media which differ radically from sea water in potassium content. Neither KCl nor CaCl 2 can replace NaCl, and increased levels of KC1 do not mitigate the inhibitory effects of high concentrations of NaCl. The fungus grows well at 12–25 C and gives maximal yields when provided with cellobiose or the cleavage products of starch as carbon sources.