The results suggest that the two loci metE+ pyrD+ are not closely linked. The closely linked loci would be expected to be cotransduced; the greater the cotransduction frequency, the closer the loci are. Because only 1 of 858 metE+ was also pyrD+, the genes are not closely linked. The lone metE+ pyrD+ could be the result of cotransduction, or it could be a spontaneous mutation of pyrD top pyrD+, or the result of coinfection by two separate transducing phages.