Since mA strain, one of the isolates from the bronchial tract of normal mice, grows readily in the PPLO broth and produces hemolysin, the biological studies on this strain will help a foundamental understanding of M. pneumoniae on which our experiments are being carried. At present, we described about the isolation of PPLO from the mice, and the growth characteristics and some biological properties with mA strain. The results are summarized as follows.
1) PPLO was isolated from 16 cases out of 31 normal 10-month-old mice and none out of ten 3-week-old mice. All of the isolates were recovered from the bronchial tract and none from the heart blood. The titer of the PPLO in 10% suspension of the bronchial tract from which the PPLO was successfully isolated was between 104 and 105 per ml.
2) The growth of mA strain in Chanock's PPLO broth was excellent. The maximum titer reached 108 per ml by 2nd day after inoculation, then the titer decreased rather rapidly and the viablity was lost completely by 8th day.
3) Carbohydrate utilization pattern of mA strain was the same as that of M. pulmonis.
4) The mA strain did not grow in an anaerobic condition and produced α hemolysin for the guinea pig red blood cells.