The investigations concerning biological properties of Mycoplasmas were carried out from the points of view of heat, pH and shaking stabilities. The Mycoplasma strains used were M. pneumoniae CL. FH, M. orale N-1, and M. salivarium-C Hup 127. M. orale N-1 was kindly supplied by Dr. Hayflick, who isolated this strain from human leukemia patients by direct agar method. These mycoplasma suspensions were tested in the resting states.
The results obtained were as follows:
1) Resitance of three strains to heat was generally labile, especially that of M. orale was markedly thermolabile; it was inactivated at 50°C for 30min. The other two strains was throughly inactivated at 55°C for 30min.
2) Stability of strains to pH is characteristic; Mycoplasmas, in general, were very weak to acid, but fairly stable to alkali. M. pneumoniae and M. orale survived for 48 hours in pH 7.76. M. orale survived for 24 hours even in pH 8.9.
3) It was interesting in the case of stability of strains to shaking that Mycoplasmas were not destroyed by shaking of 150 rev. per min., but M. salivarium and especially M. orale increased their viable units, that is, the number of colonies increased by shaking, comparing with that under the stational condition.