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Abstract
SUMMARY: The synthesis of flagella by Salmonella typhimurium was used in a study of factors affecting the formation of a single protein. Regeneration of flagella by mechanically deflagellated organisms was completely inhibited by 2 : 4-dinitrophenol (0·001 m), but not by sodium azide (0·004 m), or by sodium arsenate (0·002 m). Ultraviolet (u.v.) irradiation or treatment with nitrogen mustard in a dose sufficient to result in a 99·99 % decrease in viable count, completely inhibited regeneration of flagella. None of the amino acid, purine or pyrimidine analogues tested, with the exception of p-fluorophenylalanine, prevented the regeneration of functional flagella, although many of them inhibited bacterial growth. Flagella synthesized in the presence of p-fluorophenylalanine were non-functional and the flagella wavelength was half that of the control. Growth of S. typhimurium at 44° resulted in a progressive decrease in the number of flagella/bacterium. On continued incubation at 44° the culture became non-motile. Subsequent incubation at 37° resulted in the recovery of motility after a lag about equal to the mean generation time of the bacteria. Addition of 2-thiouracil or 8-azaguanine to a non-motile culture immediately after transferring from 44° to 37° prevented the recovery of motility. When the addition of 8-azaguanine was delayed for 1 hr. after transferring from 44° to 37°, there was no inhibition of recovery of motility. The growth of S. typhimurium at 37° was not completely inhibited by 2-thiouracil (0·001 m) or 8-azaguanine (0·001 m), but there was a fall in no. flagella/bacterium after the addition of the analogue. Since regeneration of flagella occurred at 44°, these data were interpreted as indicating that the systems responsible for the formation of flagella were absent from cultures grown at 44°, but were synthesized during the lag before the appearance of flagella on transferring the culture to 37°.
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