ARTIFICIALLY INDUCED MUTANTS OF THE GLUTAMIC ACID PRODUCING MICROORGANISMS BREVIBACTERIUM KETOGLUTAMICUM, CORYNEBACTERIUM HYDROCARBOCLASTUS, AND ARTHROBACTER PARAFFINEUS WHICH ARE CAPABLE OF GROWING ON AN AGAR MEDIUM CONTAINING SUBSTANCES HAVING PENICILLIN ACTIVITY IN AN AMOUNT CORRESPONDING TO MORE THAN 5 INTERNATIONAL OR U.S.P. PENICILLIN UNITS PER MILLILITER HAVE BEEN FOUND CAPABLE OF ASSIMILATING HYDROCARBONS AND THEIR OXIDATION PRODUCTS AS THE PRINCIPAL SOURCE OF CARBON FROM A NUTRIENT MEDIUM CONTAINING PENICILLIN-ACTIVE SUBSTANCES IN HIGH CONCENTRATIONS, AND TO CONVERT THE ADDIMILATED MATERIAL TO L-GLUTAMIC ACID RELATIVELY RAPIDLY UNTIL CONCENTRATIONS OF MORE THAN 7 G./DL. ARE REACHED IN THE MEDIUM.