Question

A new disease caused by certain strains of Salmonella is described. Studies show that the bacterium makes a protein toxin, yet no previous isolates of the Salmonella make that type of toxin. Which process most likely accounts for the Salmonella newly acquired ability to make a toxin?

A) Restriction modification

B) Horizontal gene transfer

C) Induced mutation

D) Infection by a viable lytic phage

E) Spontaneous mutation

Answer 1

If salmonella is producing a new type of toxin then there is a chance if it has interacted with another bacterium secreting the same toxin. Horizontal gene transfer is not the possibility if this strain got new properties of genes because no salmonella is been found with the same toxin properties. Restriction modification is not correct because it is the defense system used by the bacteria. Infection with lytic phage is not correct because it does not make sense if prophage bacteria get inserted in the bacterial genome. Spontaneous mutation arise that can alter the mRNA sequence and ultimately to the protein sequence. So correct answer is E.