336 Marine Microbiology 



In an analysis of the species distribution in the various 

 areas studied (Table 1), C. parapsilosis was found to be the most 

 ubiquitous yeast in Florida waters, it was common in the waters 

 and sediments of the estuary and was the most abundant off- 

 shore form. C. tropicalis and R. mucilaginosa were the most 

 numerous estuarian yeasts. In distinct contrast, however, none of 

 these species were isolated from Pacific waters. Metsclinikowiella 

 zobellii and M. krissii, described by van Uden and Castelo Branco 

 (18), were predominate among the yeasts isolated near La Jolla, 

 California. Yeasts with a similar morpholog)' have been observed 

 as parasites in the fresh-water crustacean Daphnia magna by 

 Metschnikoff (14) and in larvae of the peratogonid fly Dasyhelea 

 ohscura by Keilin (7) but were not cultured for further study. The 

 minimum number of viable cells for M. zobellii ranged from 20 to 

 580 cells per liter of sea water and for M. krissii from 10 to 570 

 cells per liter. High counts of M. zobellii were obtained from fish 

 intestines and giant kelp. These findings suggest that M. zobellii 

 and M. krissii are well adapted to marine environments. 



Since yeasts appear to be relatively common in the sea, 

 they are undoubtedly ingested during the normal feeding activi- 

 ties of fish. Examination of a variety of genera of fish from Bis- 

 cayne Bay and Bahamian coastal waters revealed that yeasts 

 appear to be restricted both quantitatively and qualitatively in 

 the intestinal tract of most fish. Although a wide variety of species 

 of yeasts were isolated ( Table 3 ) , the intestinal yeast flora of any 

 particular fish may be a reflection only of recent habitats and 

 feeding habits. In contrast to the scarcity of yeasts in the intes- 

 tinal tract of fish from Atlantic waters, two species of fish, 

 {Atherinopis affinis littoralis and Trachurus symmetricus) from 

 tlie Pacific consistently maintained higher numbers of yeasts in 

 the intestinal contents than were observed in the surrounding 

 water. The predominate species was M. zobellii with cell num- 

 bers ranging from 25 to 5,700 cells per ml or gut contents. Counts 

 for other yeast species inhabiting the intestines ranged from 5 to 

 380 cells per ml. These results suggest that some yeast species 

 appear capable of growth in the digestive tract of certain marine 

 fish. 



