SOME ASPECTS OF THE PHYSIOLOGY AND BIOCHEMISTRY OF MARINE FUNGI
Authors: JENNINGS D. H. 
Published: January 2008

1. This review deals with certain aspects of the physiology and biochemistry of marine fungi. Though it is not easy to define what is meant by a marine fungus, the information presented here relates to those species that by consensus can be accepted as being truly marine. The material is in two parts, that relating to the higher fungi (Ascomycotina, Basidiomycotina and Deuteromycotina) and that relating to the lower fungi, particularly those zoosporic fungi that require sodium for growth.

2. Higher marine fungi appear to have a similar carbon, nitrogen and vitamin nutrition to their terrestrial counterparts.

3. Growth of higher marine fungi can be optimal in 100% sea water, but more frequently optimal growth is at a lower percentage. The percentage giving optimal growth may be determined by the rate of ion uptake required to generate the necessary turgor for growth. The tolerance of the vegetative phase of many terrestrial fungi to salinity appears little different from that of marine fungi. In general, members of the Basidiomycotina are particularly sensitive to salinity, while those of the Ascomycotina and Deuteromycotina are much more tolerant.

4. The degree of tolerance to salinity may be dependent upon temperature and whether or not adaptation by the fungus has occurred.

5. Maintenance of a suitable internal potassium concentration by a higher marine fungus is important for growth in a saline medium. Calcium appears to be necessary for the retention of potassium and organic solutes within the hyphae.

6. It appears that higher marine fungi are able to maintain a ratio of potassium: sodium higher than that of sea water by the presence of a plasma membrane ATPase which may have a higher pH optimum than the equivalent enzyme from terrestrial counterparts.

7. Higher fungi produce more glycerol as the salinity of the external medium is increased. Whether or not the compound is involved in osmoregulation has yet to be determined.

8. Turgor is thought to be generated in higher marine fungi growing in sea water by organic solutes (predominantly glycerol and arabitol) and by ions, with the latter playing the major role. Though interpretation of the data depends on several assumptions, the high concentrations of sodium that seem likely to be present in hyphae or cells have implications for the activity of enzymes, if they have similar properties to those of higher plants. There is a need for information on the effects of high concentrations of ions on enzymes located in the cytoplasm of higher fungi.

9. In spite of some experimental uncertainties, it seems that reproduction and spore germination of higher marine fungi are very much less affected by salinity than are the same processes of terrestrial counterparts.

10. The zoosporic marine fungi require sodium for growth. Though the ion is required at high concentration for growth, sodium cannot be replaced by potassium. Evidence indicates that sodium is involved in the transport of solutes across the plasma membrane.

11. The carbon and nitrogen requirements for the growth of the zoosporic marine fungi demand further investigation, particularly at the biochemical level. There is evidence that the respiration of these fungi possesses many interesting features.

12. Vitamin requirements of the zoosporic marine fungi depend on the isolate under investigation. Vitamin B., does not now seem to be an obligatory requirement. The ability of phospholipids and sterols to stimulate growth requires further investigation.

13. Further studies on marine fungi in the laboratory should focus particularly on growth in continuous culture. Physiological and biochemical studies would be helped by more precise guidance from those concerned with the ecology of these fungi.