“…Native resistance of most fungi to commonly used analogs is well documented (LEMKE 1969;LEMKE and BRANNON 1972). Since penicillins and cephalosporins are derived from oc-aminoadipic acid, cysteine, and valine, it was suggested that deregulation of these amino acid pathways might lead to the selection of superior strains (DREW and DEMAIN 1977;DE-MAIN and MASUREKAR 1974;ELANDER and CHANG 1979). Recently, MEHTA and NASH (1979) showed that the relationship between the carbon source in test media markedly influenced the toxicity of a number of amino acid analogues in a highproducing strain of A. chrysogenum.…”