VI. ESTIMATION 25 



Lampcii and Pet(M'soM^^ ha\'e described a rapid turbidinietric method 

 involving a basal medium eontaiiiiiig Xorit-treated casein as the only 

 semipurified component. Anaerobic conditions for the growth of Clostridium 

 acctobutylicum were established l)y the use of sodium hydrosulfite (Xa..Sj()4) 

 and reduced iron as components of the basal medium, and \)y incubating 

 the assays in an "oat jar," where respiration of the oats estabhshes a par- 

 tial pressure of COo. The assay range is apjjroximateh^ 0.3 to 1.5 m7 of 

 PAB.\ per 10-ml. culture tube. Lampen and Peterson, confirming other 

 investigators, found PABA to exist in many natural materials, including 

 water-soluble products in microbiologically unavailable forms. They re- 

 ported that combined PAB.V may be released by alkaline hydrolysis but 

 that strong acid hydrolysis destroys PABA. 



Housewright and Koser^^ utilized Clostridium acetotmt ijlicum for PABA 

 determination with a basal medium containing all purified components. 

 .\naerobic conditions for the assay were established by alkaline pyrogallol. 

 A number of compounds related in structure were examined by House- 

 wright and Koser for microbiological activity. p-Nitrobenzoic acid, p- 

 aminobenzoylglycine and p-nitrobenzoylglycine are essentially as active as 

 PAB.\. Certain other related compounds are considerably less active. As 

 with Acetohader suhoxijdans, less PABA is required for maximum growth 

 when the basal medium contains added purines (adenine, guanine, and 

 xanthine). The microbiological method was applied to a study of PABA 

 synthesis by sulfonamide-sensitive and sulfonamide-resistant strains of 

 Staphylococcus aureus. The findings of Landy et aZ." and Spink et al.^^ that 

 resistant strains produce considerably more PABA were confirmed. 



Mirick^" has proposed the use of a pseudomonas organism isolated from 

 soil for the highly specific determination of PABA. A specific adaptive en- 

 zyme is formed by this organism which oxidizes PABA presumably to CO2 , 

 H2O, and XH3. Diazotizable amine is determined on samples before and 

 after the action of the enzyme. The difference obtained is attributed to 

 PAB.A. A few related compounds are attacked by the enzyme, but none 

 of the compounds thus oxidized undergoes the diazo reaction. The main 

 limitation of the method is primarily a matter of sensitivity of the diazo 



'' S. D. Rubl)0 and J. M. Gillespie, Xature 146, 838 (1940). 



'^J. (). I..ami)en and W. li. Peterson, ./. Am. Chem. Soc. 63, '22s:i (1041). 



■ C. H. Park and W. U. Wood, Jr., Bull. Johns Hopkins Hosp. 70, 19 (1942). 

 '^ J. O. Lampen and VV. II. Peterson, ./. Biol. Chem. 153, 19.3 (1944). 

 " R. D. Housewright and S. A. Koser, ./. Infectious Diseci.^es 75, 1 1:'. (1944). 

 "G. S. Miriok, J. Exptl. Med. 78, 255 (1943). 

 " S. D. Rul)l)o and J. M. Gillespie, Lancet, I, 36 (1942). 

 " O. Wy.ss, M. Ruhiii, an.! F. H. Straiidskov, Proc. S«c. E.rpll. liinl. Mr, I. 52, 1.').") 



(1943). 

 " J. O. Lampen and \V. 11. Pctenson, Arch Biochcm. 2, 443 (1913). 



