66 Perspectives in Microbiology 



until recently, progress in the analysis of enzymatic mech- 

 anisms in bacteria has been relatively slow. An additional 

 impediment for the microbiologist was the lack of good 

 methods for preparing enzymatically active cell-free ex- 

 tracts from bacteria. This difficulty has now been largely 

 overcome by development of the alumina grinding (16), 

 sonoration, and other techniques of preparing bacterial ex- 

 tracts. As a result of this, together with the continually in- 

 creasing interest in intermediary metabolism and the de- 

 velopment of basic knowledge of enzymatic mechanisms, 

 research on bacterial enzyme systems has expanded tre- 

 mendously during recent years. The new generation of 

 microbiologists and biochemists is now vigorously attack- 

 ing the many meaty problems of bacterial metabolism. 



Nutritional methods have also been applied extensively 

 for the study of the synthetic capacities and biosynthetic 

 mechanisms of bacteria. The study of bacterial nutrition 

 has led to the detection and isolation of a number of com- 

 pounds or growth factors which are essential components 

 of the enzymatic machinery of all or most living organisms, 

 but which are specifically required as nutrients only by 

 those organisms that are unable to synthesize them from 

 simpler substances. The nutritional approach to the study 

 of the biosynthetic pathways of amino acids, growth factors, 

 and other cellular constituents has been enormously stimu- 

 lated by the discovery of methods of effectively blocking the 

 chemical reactions of the cell so as to cause the accumula- 

 tion of various compounds in the chain of synthetic re- 

 actions. Such blocking can be achieved by the isolation of 

 appropriate biochemical mutants by modification of the 

 methods first developed by Beadle and Tatum, or by the 

 use of more or less specific chemical inhibitors. Much of 

 our present knowledge of biosynthetic pathways in bacteria 

 is based upon the use of these and related methods. 



Many other new methods and techniques have smoothed 

 the way for the student of bacterial metabolism. Of these, 



