296 Marine Microbiology 



showed no well-defined peak. At low temperatures, peaks were 

 never sharp, but the curves were generally higher in the lower 

 osmotic ranges. The optimum concentration for best growth at 

 a given temperature varied with the osmotic pressure of the solu- 

 tion regardless of its nutritive or ionic nature, or of its ability 

 to penetrate cytoplasmic membranes. Osmotic pressure thus ap- 

 pears to be the factor responsible for the relation between high 

 temperature and high solute concentration. The osmotic optimum 

 is in turn determined by temperature. 



The fact that the relation between salinity and temperature 

 is a function of osmotic pressure adds support to the idea that 

 a sort of biological principle of LeChatelier is operating. This 

 means that if one supplies an organism with sufficient added 

 energy in the form of heat, a balancing force in the foiTn of in- 

 creased osmotic pressure becomes necessary if growth is to con- 

 tinue. The requirement for higher osmotic values continues with 

 rising temperature until some critical portion of the system 

 breaks down. Moreover, the requirement for increased osmotic 

 pressure with increasing temperature is greater above than below 

 the optimum temperature for growth. In sea water media, be- 

 tween 6 C and 25 C, the optimum osmotic pressure rises only 

 slightly. From 25 C to 30 C, the optimum rises from about 20 

 Atm to about 40 Atm, an increase of 20 Atm in five degrees. 

 This relation holds generally for other organisms which demon- 

 strate the Phoma pattern (7). It must be recognized at the same 

 time that the response to increased heat energy is controlled 

 by genetic factors since, even among those organisms collected 

 in marine habitats, not all show it. Collections of fungi from 

 coastal waters of Delaware, New Jersey, and New York have 

 yielded several Alternaria, and other fungi commonly found in 

 the sea, which do not tolerate higher salinities when the tempera- 

 ture is increased. 



When Z. eistla was cultivated on a subsistence medium and 

 temperature and salinity (as sea water) were varied, the general 

 pattern of the curves was the same as when ample nutrient was 

 supplied, but the optimum temperature for growth dropped 

 from 25 C to 20 C, and growth at 30 C was poor. When the 

 fungus was cultivated on an erythritol medium containing an 



