METABOLISM OF MICROORGANISMS 



375 



places and eventually reflect back to the original point of interference. 

 It would probably be more correct to think of metabolism as a cycle 

 rather than a chain of events. 



Penicillin is specifically and irreversibly bound by gram-positive bac- 

 teria. For example, 0.49 units of penicillin per gram of dry weight 

 are bound by cells of Bacillus cereus. Extracts of the cells also bind 

 the penicillin, and it should be possible to identify the substance in the 

 extract that possesses binding power. It may be that the reaction between 

 penicillin and this cell constitutent is the primary reaction and other 

 effects are secondary. 



A well-defined effect of penicillin on nucleic acid metabolism is reported 

 by Park. This is the accumulation of uridine-5'-pyrophosphate complexes 

 in cells of Staphylococcus aureus that have been treated with penicillin. 

 In addition to uracil, ribose, and phosphoric acid, one of these complexes 

 contains an N-acetyl amino sugar. A second complex contains L-alanine 

 in addition to the other four components, and a third has attached to 

 it a peptide made up of DL-alanine, L-lysine, and D-glutamic acid. Prob- 

 ably the accumulation of these complexes is a secondary effect caused 

 by the blocking of some reaction that utilizes the uracil compounds. 



From the discussion given, it is evident that the specific effect of 

 penicillin is still undetermined. However, since many able investigators 

 are attacking the problem, distinct progress toward its solution may be 

 expected. 



Tetronic Acids. The production of a series of compounds closely 

 related in structure is a characteristic feature of mold metabolism. Be- 

 sides the penicillins, another such series is the tetronic acids. 



HO-C==C-H(R') 



(R)II-CH.-C^ C=0 

 H 



1. y-Methyl tetronic acid, Penicillium charlesii. 



2. Carolinic acid, P. charlesii: 



R' = CO(CHo)oCOOH (succinyl group). 



3. Carolic acid (+HoO), P. charlesii: 



R' = C0(CHo)2CH.0H (y-hydroxybutyryl). 



4. Terrestric acid (+HoO), P. terrestre : 

 R' = CO(CHo)2Ch6h • C0H5 



(an ethyl derivative of the R' group in carolic acid) . 



5. Dehydrocarolic acid (+H2O), Pe?iza7/iwm cinerascens: 

 CH3— of carolic acid is replaced by CH2= 



6. CarHc acid, P. charlesii: 



R = HOOC; R' = CO(CH2)2CH20H (y-hydroxybutyryl) 



7. Carlopic acid, P. charlesii: 



R = HOOC; R' = CO- CH0CH2CH3 (butyryl). 



