PHYSIOLOGICAL-STUDIES ON GENTAMICIN - PHOSPHATE REPRESSION OF ANTIBIOTIC FORMATION

The effect of inorganic phosphate on the fermentative production of ge ntamicin by Micromonospora purpurea has been studied using a chemicall y defined medium. Phosphate concentrations higher than 5.75 mM (1 g/li ter(-1)) did not inhibit growth but specifically prevented antibiotic formation. Changes in the pH medium and carbon or nitrogen depletion w ere excluded as the cause of antibiotic underproduction. The use of a phosphate analogue, a protein synthesis inhibitor and the profiles of differential rate of antibiotic production suggested that phosphate it self transiently repressed gentamicin formation. Phosphate affected th e formation of 2-deoxystreptamine from 2-deoxyinosose, a none phosphor ylated substrate.