Yeasts isolated from the intestine of rainbow trout adhere to and grow in intestinal mucus.

The yeast strains Saccharomyces cerevisiae CBS 7764 and Debaryomyces hansenii Hf1 (CBS 8339), isolated from the intestine of rainbow trout, were studied with respect to adhesion to and growth in fish intestinal mucus. The level of adhesion was dependent on the physiologic state of the yeast culture. Growing cells of both strains adhered more strongly than nongrowing cells. This correlates with a previously shown shift in cell surface hydrophobicity of these yeasts. In addition, forces other than hydrophobic interactions may participate, as all strains tested adhered more strongly to the membrane lipid phosphatidylserine than to phosphatidylcholine and phosphatidylethanolamine. Debaryomyces hansenii Hf1 also adhered to the most hydrophobic of the neutral lipids present in mucus, while no adhesion was observed to the other neutral lipids or to the hydrophilic silica gel, again suggesting hydrophobic interactions. Finally, the fish-isolated yeasts grew rapidly in isolated fish intestinal mucus as the sole source of energy and nutrients.