Biosynthesis of Nitrogen-Containing Compounds

Nitrogen is essential for growth in all biological systems, and its assimilation into a variety of life-sustaining compounds has been the topic of study for many microbiologists. This chapter focuses on ammonia assimilation and the biosynthesis of amino acids, polyamines, pyrimidines, and purines. Wherever possible, emphasis will be directed toward findings obtained from ruminai and colonic bacteria, although the knowledge base developed for these bacteria is relatively superficial. To overcome these limitations, some discussion pertaining to gramnegative enteric bacteria (Escherichia coli, Salmonella typhimurium [official designation, Salmonella enterica, serovar typhimurium], and Klebsiella spp.) and gram-positive bacteria (Bacillus subtilis and Clostridium spp.) has been included for the sake of clarity and reference. Readers interested in detailed information concerning the topics covered in this chapter, as well as the biosynthesis of nitrogen-containing vitamins and coenzymes, should refer to the volumes edited by Neidhardt et al. (1996) and Sonenshein et al. (1993), as well as the recent review of nitrogen control in bacteria by Merrick and Edwards (1995). The goals of this chapter are to provide a cohesive overview that complements the well-chronicled field of knowledge developed from these intensively studied species, and to highlight opportunities where further studies of ruminai and colonie bacteria may expand our understanding of these processes.