Studies on the relationship of pteroylglutamic acid to the growth of psittacosis virus, strain 6BC.

p-Aminobenzoic and pteroic acids antagonize the inhibition of the growth of psittacosis virus (strain 6BC) by sulfadiazine in a competitive manner. Pteroylglutamic acid exerts a non-competitive type sulfonamide antagonism. The effects of certain analogues of pteroylglutamic acid and of pteroic acid on the growth of psittacosis virus and its inhibition by sulfadiazine are reported. The implications of these findings with regard to the possible synthesis of pteroylglutamic acid by psittacosis virus and its suggested rôle as an essential factor for growth of this virus are discussed.