SIMULATED IN-SITU COMPETITIVE ABILITY AND SURVIVAL OF A REPRESENTATIVE SOIL YEAST, CRYPTOCOCCUS-ALBIDUS

Microcosms containing an air-dried autoclaved loamy sand (Eufala A) wi th low salt and organic content were inoculated with a representative (obligately aerobic, encapsulated) soil yeast, Cryptococcus albidus va r. albidus(T) ATCC 10666, singly (for growth rate and survival determi nations) and together with the bacterial biota native to Eufala A. The yeast competed successfully with the more rapidly growing bacteria in the presence of added water from 1% (5.7% of field capacity) to 14% ( 80% of field capacity) but grew for shorter times than when grown alon e; times correlated with the lag phase of the bacterial biota. When we ll-watered (10 and 14%) competition cultures were allowed to dry and u sed as inoculum for subcultures, the yeast made significant growth onl y at 1% added water but survived at the higher moisture concentrations . The competitive ability of Cr. albidus confirms the previously repor ted advantages of the cryptococcal capsule in hydration and desiccatio n and, together with lengthy survival, suggests that the importance of such yeasts in the biogeochemistry of arid soils has been seriously u nderestimated.