RESPIRATION OF A COLORLESS FLAGELLATE, ASTASIA KLEBSII

¹ Physiology Department, Georgetown University Medical School, Washington, D. C.

1. Concentrated cell suspensions of Astasia klebsii were prepared from pure cultures. The respiration of these suspensions was measured by the Warburg direct method at 25.2° C., usually at pH 5.8.

2. Cells, in inorganic medium showed an early period of declining respiration, followed by an approximately constant period. During the constant period, old (stationary-phase) cells consumed about 1.9 cu. mm. O₂/hour/million, cells, and young (logarithmic-phase) cells consumed about 3.8 cu. mm. O₂/hour/million cells.

3. The effects of numerous organic compounds on respiration were tested. Only formate, acetate, propionate, ethyl alcohol, and hexosedi-phosphate produced a definite increase in oxygen consumption, the greatest increase occurring in acetate.

4. In inorganic medium, respiration was approximately the same between pH 4.5 and pH 7.9. In acetate, respiration was the same at pH 5.8 and pH 7.9, and much lower at pH 4.5.

5. In acetate the respiratory quotient was 1.0; in inorganic medium it was slightly less than 1.0.

6. The presence of cytochrome in the cells was detected by spectroscopic examination.

7. The highest non-toxic concentration of cyanide (M/100) produced about 95 per cent inhibition of respiration in acetate, and a lesser degree of inhibition in inorganic medium. The highest non-toxic concentration of azide (M/1000) inhibited nearly 90 per cent of the respiration in acetate, but had no inhibitory effect on respiration in inorganic medium.