Relationship between carbon source and susceptibility of Cephalosporium acremonium to selected amino acid analogues.

The susceptibility of Cephalosporium acremonium to selected amino acid analogues was markedly influenced by the carbon source used in the test media. Lysine hydroxamate, beta-hydroxy norvaline, and hexafluorovaline were toxic when tested with ribose, ribose or fructose, and ribose or galactose, respectively. In contrast, thialysine and thiaisoleucine inhibited C. acremonium with glucose, fructose, galactose, sucrose, mannitol, sorbitol, and soluble starch. Neither of these analogues was toxic at levels tested when glycerol was used as a carbon source. The minimal inhibitory concentrations (MIC) of thialysine, homoserine, and alpha-methylserine were greater than 1000, greater than 1000, and 250 microgram/mL, respectively, with glycerol. In contrast, the MIC values for the same three analogues were 31, 62, and 125 microgram/mL, respectively, with mannitol. The matching of the carbon sources with the specific amino acid analogues expands the number of analogues useful for selecting derepressed mutants. Thialysine-resistant mutants (tlysR) of C. acremonium which excrete lysine were isolated on a medium containing mannitol.