LEVADURAS DEL MANA PICHIA FARINOSA LINDNER

Resumen

The yeasts of this study were collecced by Professor Ochoterena in the manna that was running out of an ash tree in the gardens of Morelia.
After isolating the yeasts in a pure culture we began to study them in different media, both liquid and solid. In all of them the cells show characterists similar to the following: they form a scum, a ring or a deposit in the
liquid media; in the solid media they form colonies which are milky white, circular, have entire borders, are globular, humid and shiny; later they become gray and finally brown. They are generally elongated, some being elliptical and ovoid ; they are 12 microns long and 3 to 4 microns wide. In the protoplasm can be seen vacuoles, a few drops of oil and metacromatic granules.
By using special dyes we were able to diferentiate the nucleus with its chromatin and nucleolus, the metacromatic granules, the oil and the glycogen.
The maximum temperature of growth is from 38° to 40°; the optimum from 24° to 27°, and the minimum from 3° to 5°. The maximum temperature for the formation of the scum is 37° ; the optimum 25° to 28°, and the
minimum 5° to 8°.
Ascospores are formed easily in almost all of the media, specially in the scum, but apparently loose this property when the cells are cultivated in media with gelatine. There are from 1 to 4 ascospores in each asc ; they are circular or ovoid, 2 to 3 microns in diameter and have a shiny granule in the center. According to the illustrations of Lindner and Saito it seems that the ascs are formed by a copulation ; but Guilliermond showed that the illustrations of these authors represented simple buds; we arrive at the same conclusions.
These yeasts ferment glucose and levoluse weakly, but has no reaction on the other sugars.
We identify the yeasts of the present study as Pichia farinosa, isolated and studied by Lindner in 1893.