FISH-KILLING FACTOR PRODUCED BY PROTEUS VULGARIS

III. SEPARATION OF THE TOXIC FACTOR

Abstract

1. The fish-killing factor produced in peptone solutions by Proteus vulgaris was not adsorbed by either kaolin or animal charcoal.
2. Absolute alcohol could not precipitate the factor from the culture solution, similarly with tannin and picric acid.
3. Both AgNO₃ and phosphotungstic acid could form a precipitate, leaving the culture solution non-toxic, but no active factor was liberated from the precipitate.
4. Simultaneous addition of Ba(OH)₂ and absolute alcohol produced a precipitate with which the factor was completely precipitated. The precipitate thus obtained was found to be a Ba-salt of a polypeptide present in the peptone preparation.
5. A similar precipitate was produced even when an uninoculated peptone solution was used. The polypeptide whose Ba-salt was precipitable by the addition of alcohol was presumably changed into the toxic factor by the action of the bacteria, whereby a portion of NH₂-group was dissociated from the polypeptide.
6. Sometimes the polypeptide seemed to become non-precipitable after a long duration of incubation without losing the toxic activity.
7. When CaCl₂ was used instead of Ba(OH)₂ the same result was obtained.