PREFACE 



Little reflection is required to realize that nitrogen is a 

 constituent of numerous compounds of biological interest, 

 and all acquainted with present-day biochemistry are aware 

 that during the last ten years the former emphasis on the 

 study of the degradation of complex substances has been 

 largely replaced by an active interest in mechanisms of syn- 

 thesis, and in particular, in the synthesis of proteins and the 

 metabolic role of the nucleic acids. Micro-organisms are 

 proving to be of great value in the unravelling of the routes 

 whereby amino-acids, nucleotides and other compounds are 

 synthesized in mvo, and for a long time they have been used 

 with great success in experiments designed to elucidate the 

 functions of the many water-soluble substances now in- 

 cluded in the B group of vitamins. 



In this monograph an attempt has been made to survey 

 as comprehensively as possible the nitrogen metabolism of 

 micro-organisms and to treat the subject in such a manner 

 as to reflect current trends in modern microbiology. The 

 monograph is based on a series of lectures given in a one- 

 year post-graduate course of microbiology held in the Uni- 

 versity of Sheffield, and it is hoped that advanced students 

 at other universities and research workers in allied fields will 

 find it a convenient and concise introduction to one impor- 

 tant section of microbial biochemistry. If it be thought that 

 some topics receive more attention than they warrant, then 

 the author accepts full responsibility for his choice and de- 

 fends it on the grounds that these topics either encompass 

 ideas of wider significance or serve to focus attention on how 

 little has really been established. Though the title of the 

 monograph is all-embracing and in the text examples are 

 drawn from experiments with bacteria, fungi, algae and pro- 

 tozoa, the m.ain emphasis is naturally on the first two of these 

 four groups, since most work has been done with species of 

 bacteria and yeasts. There is not space to mention every 



