Transduction of Multiple Nutritional Requirements in Salmonella Typhimurium

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Abstract
Multiple auxotrophs were obtained from S. typhimurium by successive X-ray or u.-v. radiation exposures of the wild types 533 and 549, for use in transduction expts. whereby a filterable agent (FA) liberated by certain Salmonella strains can transfer individual traits from a donor strain to other susceptible strains. Two strains, which were stable with respect to normal reversion rate, were used in transduction tests. A description of the procedure used is given. When a mutant of 549, requiring threonine, proline, isoleucine and valine, was grown in the cell-free filtrate of a mutant of 533 requiring arginine, methionine and asparartic acid, strains were isolated with many different combns. of the requirements of the parental strains, whereas no new types were found when the mutant of 533 was grown in the filtrate of the mutant of 549. When an isolate (from this expt.) requiring methionine, aspartic acid and proline was tested with a multiple mutant of 533 requiring leucine, threonine and tryptophan, the 533 mutant was susceptible to the FA activity from the isolate, but 533 filtrate caused no change in the isolate. More transduced forms appeared after the susceptible strain was grown in an active filtrate than when the two strains were grown together. The method used does not test for all combinations of nutritional requirements and does not indicate what proportion of the total no. of organisms in the suspension show transduction. The data show that transduced requirements are individually detd., but that from 1 to 6 different requirements may be produced in a single bacterium. The ability to cause transduc-tions is limited to a few donor strains of Salmonella which are selective in their action.

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