SUMMARY: The effect of various conditions on the rate of death of and of in dilute buffer solutions was followed by making colony counts at intervals during prolonged periods of incubation and then constructing mortality curves. The form of these curves was characteristic for each organism. Of the pH values investigated (approximately 5, 6, 7 and 8) both organisms were least viable in the range 6 to 7. was not affected by the degree of oxygenation of the water but died much more rapidly under anaerobic than under aerobic conditions.

Growth of was observed with as little as 0.28 part per million organic matter in solution. A much higher concentration of nutriment was required for growth of ; with a concentration slightly below that required for growth the viable population remained virtually stable for a long period. The rate of death depended on the age of the cells at the time of immersion in water.


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