ANAEROBIOSIS-INDUCED DIFFERENTIATION OF ACANTHAMOEBA-CASTELLANII

Acanthamoeba castellanii is a free living amoeba ubiquitous in soil an d also commonly found in aquatic environments. In waterlogged soils; a noxia is quickly established as the dissolved oxygen is consumed by th e organisms present. We were interested in the effects of anoxic condi tions upon this organism. Batch cultures degassed with N-2 during mid- exponential growth, induced encystation within 12 h of anoxia, and mat ure cysts were formed within 2-3 days. Excystation (99%) was achieved by subsequent aeration of these cultures after 3-6 days. Anoxia-induce d cysts, maintained in anoxic conditions for up to four months, remain ed viable. Difference spectra, during anaerobiosis, revealed that cyto chromes were not lost, suggesting that the organism retains its respir atory components. The growth rate of trophozoites, grown in a chemosta t, was dependent on the concentration of O-2 in the head space and glu cose uptake increased at lower dissolved O-2 tensions. The results obt ained suggest that A. castellanii has a complex adaptive strategy enab ling it to cope with microaerobic and anoxic conditions which may be e xperienced in the environment.