Utilization of Amino Acids and Other Nitrogen-Containing Compounds

This chapter discusses the catabolism of amino acids and other nitrogen-containing compounds. Aspartate is transported into B. subtilis by two systems, a high-affinity system energized by the proton motive force and a low-affinity system. The enzymes of the arginase degradative pathway are found in B. subtilis and B. licheniformis. In B. subtilis and B. licheniformis, the proline-degradative enzymes are induced by proline. In B. subtilis, this induction is inhibited if the growth medium also contains glucose and amino acids. Hut expression in B. subtilis is induced by histidine and repressed by rapidly metabolized carbon sources such as glucose. Growth in the presence of amino acids severely inhibits synthesis of the Hut enzymes. Dehydrogenase enzymes may play a role in the degradation of phenylalanine in Bacillus badius, of valine in Streptomyces spp, and of leucine in B. cereus. Nitrate reductase activity is found in B. subtilis cells growing in the presence of nitrate under semianaerobic conditions. Amino acids and small peptides produced by the degradation of extracellular polypeptides can also supply B. subtilis with nutrients during growth and sporulation.