Strategies for osmoregulation in the marine fungus Cirrenalia pygmea Kohl. (Hyphomycetes)

351-358The marine fungus Cirrenalia pygmea during growth at increased salinities responded by increasing its intramyceliar polyol content. A similar response was noticed when the fungus was exposed to sudden hyper-osmotic shock; this response was irrespective of the osmotic substance (ionic or nonionic) present in the growth medium. A hypo-osmotic shock treatment led to a decrease in the polyol content. Increasing salinity increased the activity of polyol enzymes such as polyol dehydrogenase and mannitol dehydrogenase. These observations suggested that polyols contribute to osmotic regulation in this marine fungus. The fungus accumulated a mixture of polyols, when the mycelium aged. The sodium content of the mycelium increased with salinity, although the potassium content did not. Higher salinity also led to an increase in the amino acid pool size. Proline and Dragendorff - positive compounds were absent from the mycelium growing in higher salinities. The level of mycelial sugars decreased with increase in salinity whereas that of glycogen and sterols increased with salinity. The fatty acid profile of the fungus was also influenced by salinity. Higher salinities brought about a decrease in the extent of unsaturation of fatty acids. The melanin content of hyphae also increased with external salinity. Based on these results, a synthetic approach is attempted here to explain the various strategies evolved by this manglicolous fungus to survive in a vagarious environment