MUTANTS OF BACILLUS SUBTILIS THAT REQUIRE THREONINE OR THREONINE PLUS METHIONINE

Abstract

Of 12 mutant strains of B. subtilis studied nutritionally, 7 required only threonine; 2 required both threonine and methionine, but could utilize homoserine (alpha-amino-gamma-hydroxybutyric acid) instead; and 3 required threonine and methionine, but were unable to grow on homoserine alone. In B. subtilis. as in Neurospora. homoserine appears to serve as a precursor of both threonine and methionine. One of the threonine-methionineless (homoserineless) mutants was reverted to the "wild type" with a frequency of about 3 x 10-7 using 90,000 to 100,000 r of X-rays.