Abstract
It was previously reported 1 that from a certain multivalent Shiga phage, most Sonne strains absorbed distinctly but only the rough fraction, i. e., detectable only when a rough Shiga strain or a susceptible Sonne strain was employed in the test for residual phage. In these and earlier experiments 2 the bacteria were heated for 2 hours at 70°C.
Subsequent studies were then made with phages derived from chicken-stools and propagated with Sonne organisms. Although these phages gave equally strong reactions on all (IS) Sonne cultures available, curiously enough none of our strains heated to 70°C. showed distinct absorptive effects. This result seemed to indicate the presence of heat-labile factors. So, we compared organisms heated at 56°C. and at 85°C. for one hour. Absorption was obtained only with some strains subjected to the milder degree of heat. The nature of absorbing and non-absorbing strains could not be correlated with the above-mentioned differences in ability to absorb the rough fraction of the Shiga phage, nor with the quality of smoothness or roughness, nor with the direct titer. Indeed, from one of the absorbing strains, smooth and rough variants were obtained and both exhibited thermal lability.
In view of the stability to formalin of heat-labile antigenic (flagellar antigens) and/or phage-specific factors (V. antigen of B. typhosus (Craigie) 3 ), absorptions were made with formolized strains'.† Thus treated, only the strains that possessed the heat-labile factor absorbed from the Sonne phage and they were just as effective as the bacteria heated at 56°C.
These observations on the Shiga and Sonne phages indicate that while thermostable Sonne factors are involved in reactions with the former phage, the latter (homologous) phage reveals heat-labile bacterial components.
The Sonne phage reacted intensely also on a small number of strains of B. dysenterice Flexner, but suitable absorptive tests failed to reveal the presence of corresponding fractions of phage.
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