Ionic Relations and Polyol Metabolism of Marine Fungi in Relation to Their Environment

Abstract

The filamentous Hyphomycete Dendryphiella salina is the most extensively studied marine fungus. It has been shown by radiotracer flux analysis and X-ray microanalysis that the cytoplasmic concentrations of K, Na and Cl in mycelium gowing in 500 mM NaCl is of the order of 51–88, 74–139 and 160 mM respectively. There appears to be no accumulation of salt in vacuoles. In vivo studies of the effect of K and NaCl on enzymes are in keeping with the above values. Polyols make a major contribution to the osmotic ballast. The total concentration at any one external water potential is relatively constant. However the proportions of the four individual polyols, glycerol, erythritol, arabitol and mannitol may differ according to the solute generating the water potential. Growth of the marine yeast Debaryomyces hansenii in continuous culture suggests that polyols as well as producing compatible osmotic ballast are also, through their metabolism, involved in energy dissipation via futile cycles under conditions when growth becomes limited by conditions other than carbon supply. Primary and secondary transport in marine fungi is proton-and not sodium-based but a large volume cell wall may be involved in maintaining the appropriate proton electrochemical potential gradient.