I was very pleased to hear from you; I remember very well indeed the cordiality and courtesy afforded me during my visit some
We have tried the experiment mentioned in your letter, without much success. It is possible that pullorum and gallinarum
would need several genetic changes at once to restore motility; on the other hand transduction might not work in the same
way with these particular types. However, since every other Salmonella in groups B or D that has been tested has worked reasonably
well, I suspect the former possibility. Dr. Bruce Stocker spent a few weeks working with me last summer on transductions
of motility to various O forms (from typhi, paratyphi B, paratyphi A, typhimurium, etc.) It appears that there are several
factors all necessary for motility, and this would fit the first possible explanation of the failure with gallinarus. In
general, only single factors can be transduced at once, so that we could not restore motility to a strain requiring several
factors. Incidentally, we have thus developed a technique for "unmasking" the serotype of O forms. If you have any
stable nonmotile variants, we would be glad to try to transduce motility to them if they are in group B or D, and can use
them in future experiments if not. We are, however, in communication with Edwards at the National Center, and need not trouble
you for strains that may already have been forwarded to him.
I can give only a speculative answer to your question about host-adaptation. It seems likely that this is determined by genetic
factors which are quite distinct from the flagellar antigens, surely, and, in view of the overt equivalence of the somatic
antigens of S. typi and S. gallinarus, probably from the somatic antigens as well. Restoring or substituting the H antigen
would make very little difference. C.C. Spicer and I are now working on the technically more difficult problem of transducing
somatic antigens, and thse results might lead to a more comprehensive answer. We have been thinking of this problem, but
are not sure the present material is the most appropriate. We could compare Typhimurium, paratyphi B, and the "hybrid"
paratyphi b --x typhimurium in mice, and may sometime do this.
We have studied your question on relationships to phage action. For FA effect it is not necessary that the recipient strain
be lysed by the phage, only that the phage be adsorbed. Thus a bacterium that is already lysogenic for and resistant to a
given phage will respond to preparations of the phage grown on another host, On the other hand, one can saturate the receptors
of the bacteria at any time by adding an excess of one phage so that these cells will not adsorb, and suffer transduction
from a second phage.