Chapter 29 



The Effects of Osmotic and Nutritional 

 Variation on Growth of a Salt-Tolerant Fungus, 



Zalerion eistla 



Don Ritchie and Myra K. Jacobsohn 



Ahe "optimum" salinity for vegetative growtli in several ma- 

 rine fungi has been found to be a fluctuating value, shifting as 

 temperature shifts. In a marine Phoma, for example, the salinity 

 optimum varies from about 20 S%o ( 20 parts total solids by weight 

 per thousand parts of solution) at an incubation temperature 

 of 16 C to about 48 %o at 37 C (7). This Phoma pattern has also 

 been found in marine imperfect fungi of the genera Pestalotia, 

 Curvularia, and Zalerion. It is irregular in some genera (e.g., 

 Helicoma) and absent in others {Alternaria, Pullularia, Spicaria, 

 etc.). Fungi isolated from terrestrial habitats {Mucor, Asper- 

 gillus) and tested did not exhibit the Phoma pattern (8, and 

 Ritchie, unpublished). These data tell only that an increasing 

 temperature is accompanied by an increasing salinity "optimum,' 

 but they give no clue as to whether that optimum reflects an in- 

 creasing tolerance or an increasing salt demand, nor do they af- 

 ford any indication of the mechanism involved. 



Phoma herbarum did not grow at all at 16 C in a medium 

 containing 90 S%o while it attained a colony diameter of 36 mm 

 at 25 S per mille. At the other extreme, a marine Curmdaria did 

 not grow at all at 37 C in a medium containing 10 S%o while 

 it attained a colony diameter of 10 mm at 100 S%o. Thus an 

 increasing temperature is accompanied by an increasing salinity 

 "optimum," but the data do not show whether that optimum re- 

 flects an increasing tolerance or an increasing salt demand, nor is 

 the mechanism involved indicated. 



* Supported by the Undergraduate Research Participation Program of the National 

 Science Foundation. 



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