FIG. 1.

Methionine biosynthesis pathways in B. subtilis. Genes that are preceded by S-box regulatory elements are shown with a boxed “S.” The “y” designation in gene names indicates genes whose function has not been experimentally established; possible assignments to enzymatic steps demonstrated in K. pneumoniae (6, 19) are shown but have not yet been tested (8). The function of the ykrS gene product is not known. SAM, S-adenosylmethionine; SAH, S-adenosylhomocysteine; SRH, S-ribosylhomocysteine; MT, methylthio; KMTB, 2-keto-4-methylthiobutyrate; THF, tetrahydrofolate.