Clonal relationships among naturally occurring nicotinamide-requiringSalmonella typhimurium

Abstract

SUMMARYSalmonella typhimuriumstrains of biotype 25x have been shown in transductional cross experiments to be clonal in the Nad character. The ancestral bacterium, probably of biotype 25a, mutated to a requirement for nicotinamide and subsequently diversified in phage type and secondary biotype characters. Such a sequence of events indicates interconversion among phage types 6, 16, 46, 49, 73, 76 and 135. Strains in biotypes 1x, 9ix, 17x, 17dx, 19dx and 25hix yielded Nad+recombinants in interbiotype crosses, suggesting that each originated as an independent mutant line.