Abstract
Summary
Two killer stocks of Paramecium aurelia, 51 and 299, have been cultivated axenically in a medium consisting of vitamins, a salt mixture, stigmasterol, proteose-peptone, an enzymatic digest of lactalbumin and the nondialysable fraction of a hot water extract of yeast. All components are neeessaty for growth of the ciliates and for maintenance of the kappa character. Differences in nutritional requirements of the two stocks have been noted. As far as is known, this is the first instance of cultivation of a kappa-bearing strain of Paramecium in bacteria-free medium.
Since this paper was submitted for publication, stocks 138 and 139 of P. aurelia, containing respectively μ and π particles, have been placed in axenic culture (medium No. 8 as given in Table II). The organisms have been maintained in tube culture for two months without loss of particles.
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