338 Marine Microbiology 



is most likely that any single isolation medium will fail to support 

 growth or insure reproduction of all yeasts contained in a marine 

 sample. Evidence for this was the occasional yeast isolated in this 

 study that died out after two to three transfers on a battery of 

 media prepared with sea water. 



Contrariwise, a number of marine isolates that grow in re- 

 stricted fashion on initial isolation attained physiologic vigor 

 and demonstrated excellent growth in subsequent transfer. This 

 is exemplified by certain off-shore isolates of C. parapsilosis 

 which, as previously discussed, required a period of adaptation on 

 organically rich media before they were able to evidence fermen- 

 tation. All yeasts isolated from the sea were tested for the ability 

 to utilize for growth, carbohydrates known to occur within algal 

 cells. These strains did not demonstrate any significant metabolic 

 variations from terrestrial counterparts when grown on such 

 sugars as fucose, dulcitol, mannitol and galactose. 



In this study no yeast encountered has shown unequivocal 

 dependence on factors or conditions distinctive for the marine 

 environment, nor has any isolate fulfilled the basic requirement 

 deemed necessary to be termed a true marine form. The one 

 possible exception are species of Metschnikowiella. They appear 

 to be well adapted to life in the sea and perhaps are closer to 

 the concept of a valid marine yeast than any other species yet 

 encountered. With the information currently available, it would 

 appear desirable to define a marine yeast merely as any yeast 

 that is a consistent component of the oceanic microflora with 

 demonstrated ability to survive and reproduce in this environ- 

 ment. 



The authors wish to express their gratitude to Mr. D, G. 

 Ahearn, Mrs. C. E. Marks, Miss S. A. Meyer and Mr. S. Zellner 

 of the Dept. of Microbiology, Univ. of Miami, Florida, for their 

 help in collection and examination of materials. Throughout the 

 Florida study the advice and criticism of Dr. Frank J. Roth, Jr., 

 Dept. of Microbiology, Univ. of Miami, and Dr. S. P. Meyers, 

 Institute of Marine Sciences, Univ. of Miami, was greatly appre- 

 ciated. The senior author wishes to thank Dr. James A. Oliver, 

 American Museum of Natural History for the use of the Lemer 

 Marine Laboratory, Bimini, Bahamas. 



