On the mechanism of adaptation of micro-organisms to conditions of extreme low humidity.

Low humidity is considered one of the main obstacles for life on Mars. Mechanisms of adaptation to extreme low humidity are investigated in asporogenic yeasts. Cryptococcus albidus var. diffluens inhabits the high mountain deserts of the Pamirs and the Tien Shan. The spin-echo nuclear magnetic resonance method shows that different ways of drying do not extract all liquid water from the cells. Residual humidity of the Cryptococcus cells may reach 30%. The polysaccharide capsule of Cryptococcus delays the drying process noticeably and also collects moisture at low relative humidity. The considerable quantity of conserved liquid water allows Cryptococcus to adapt to the great periodic oscillations of relative humidity resulting from the great diurnal temperature changes in the high mountain deserts. Data obtained indicate the presence of a humidity regulating mechanism on the cellular level in lower plants.