A study of yeast populations in a waste stabilization pond system

Summary

From 40 habitats within a waste stabilization pond system for the treatment of sewage from a small institutional dormitory and dining hall, samples of sewage, sludges, pond waters and effluents, and undisturbed and disturbed soils were collected. From these samples and from samples of materials from an adjacent stream, 54 categories of yeasts were isolated in a year-round survey. Although all of the commoner species have been isolated from human clinical materials in past work, none of the species found has been associated with human disease conditions in temperate regions of the northern hemisphere.

All of the commoner and some of the less-common species were isolated from shaken cultures in YNB broth, with 1% and 20% glucose used as paired media. Other species, as well as all the commoner species, were obtained on broths made of YCB and YNB media to which were added different nitrogen or carbon sources. For routine surveys of populations the shaken YNB broth cultures seem adequate, but quantitative techniques must be developed for more critical delimitation of populations.

In general, within the sets of samples tested,Candida krusei, C. tropicalis, C. parapsilosis, Rhodotorula glutinis, R. mucilaginosa, andSaccharomyces cerevisiae appear indicative of organic enrichment of waters and soils.