INTERRELATIONSHIP BETWEEN p-AMINOBENZOIC ACID AND PTEROYLGLUTAMIC ACID AS GROWTH FACTORS FOR LACTOBACILLI*

The elucidation of the structure of pteroylglutamic acid (PGA) (Lactobacillus casei factor, vitamin B,) has shown that p-aminobenzoic acid (PABA) is a component of the PGA molecule (1). Since earlier work has treated PABA and PGA as distinct growth factors for bacteria (2), it is now necessary to study the relationship in the utilization of these substances by bacteria. It has been shown that many bacteria can synthesize PGA (3-7) and in some cases this has been related to the PABA content. of the medium (5, 6). Recent findings also indicate that sulfonamides inhibit the synthesis of PGA from PABA by enterococci (8). Lactobacillus casei and Lactobacillus arabinosus have been used in the present work to study the synthesis of PGA from PABA and to show only partial replacement of PABA as a bacterial growth factor by PGA.