Regulation of staphylococcal XXXX B.

@entity2755 @entity794 @entity413 @entity31144
Several factors influenced the formation of @entity31144 B by @entity794 S-6. In the standard casein hydrolysate medium, toxin was not produced in detectable quantities during exponential growth; it was produced during the post-exponential phase when total protein synthesis was arithmetic. The rate of toxin synthesis was much greater than the rate of total protein synthesis. The appearance of @entity31144 was inhibited by @entity2755 ; thus, the presence of toxin was dependent on de novo protein synthesis. When low concentrations of @entity413 (<0.30%) were added to the casein hydrolysate medium, growth was diauxic; @entity413 was completely metabolized during the first growth period. During the second growth period, @entity31144 was synthesized. In unbuffered casein hydrolysate medium containing excess @entity413 , toxin synthesis was completely repressed. The absence of toxin production under such conditions might be explained by the low (4.6) pH resulting from the acid end products of @entity413 metabolism. At pH <5.0, little or no toxin was produced. Toxin synthesis was initiated in the presence of @entity413 when the medium were buffered at any pH above 5.6. In such media, the differential rates of toxin synthesis, with respect to the rates of total protein synthesis, were lower than the differential rates in casein hydrolysate medium alone. Addition of @entity413 to a culture synthesizing toxin resulted in an immediate decrease in the differential rate without any change in pH. Thus, toxin synthesis appeared to be regulated by catabolite repression.
