Microbial Mufanfs 



43 



COOH 



c.o 



HOOC. XH, 



1*^ * Tyrosin* 



5-Oehydroquinic S-Oehydroshikimic 

 Acid Acid 



(OHQ) (OHS) 



Anthronillic-^ -♦Indole 

 Acid 



•Trypto- 

 phan 



p-AmmobenrolC 

 Acid 

 (PAB) 



p-Hydroxybenioic 

 Acid 

 (POB) 



5-Phosphoshikimic 



FIGURE 1. Path of Aromatic Biosynthesis 



^ Mutants blocked immediately before shikimic acid ac- 

 cumulated a precursor of this compound that was readily 

 recognized as a growth factor for strains with still earlier 

 blocks. Salamon (28) isolated this precursor and identified 

 it as 5-dehydroshikimic acid (DHS). The compound that 

 in turn precedes DHS on the biosynthetic path was much 

 slower to be recognized, since mutants blocked before it, 

 in either Escherichia coli or Aerobacter, showed exceed- 

 ingly little growth response. It was eventually found possi- 

 ble, however, to obtain from these mutants secondary 

 derivatives that responded well to this compound and 

 hence could be used for bioassay during its purification 

 (12). Weiss (30) was then able to isolate the compound 

 and identified it as 5-dehydroquinic acid (DHQ). Further- 

 more, mutants of Aerobacter that could respond to this 

 substance were found to respond equally well to a well- 

 known closely related compound, quinic acid. But E. coli 

 mutants that responded to DHQ neither utilized nor ac- 

 cumulated quinic acid (12). 



