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Category: Bacterial Pathogenesis; Microbial Genetics and Molecular Biology
Utilization of Amino Acids and Other Nitrogen-Containing Compounds, Page 1 of 2
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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.
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Arginine and proline degradative pathways in Bacillus spp. The proline degradative enzymes are as follows: 1, proline oxidase; 2, pyrroline-5-carboxylate dehydrogenase. The enzymes of the arginase degradative pathway (I) are as follows: 3, ornithine transaminase; 4, arginase; 5, urease. The enzymes of the deiminase pathway (II) are as follows: 6, arginine deiminase; 7, ornithine carbamoyltransferase; 8, carbamate kinase. Glutamate semialdehyde is spontaneously converted to pyrroline 5-carboxylate, the more-stable cyclic form of glutamate semialdehyde. The last step in the arginase degradative pathway and proline degradation was reported to be catalyzed by different pyrroIine-5-carboxylate dehydrogenase isozymes in B. subtilis ( 23 ). However, the bacterial strain used in these studies ( 23 ) was subsequently found to be B. lichentformis ( 45 ).
Arginine and proline degradative pathways in Bacillus spp. The proline degradative enzymes are as follows: 1, proline oxidase; 2, pyrroline-5-carboxylate dehydrogenase. The enzymes of the arginase degradative pathway (I) are as follows: 3, ornithine transaminase; 4, arginase; 5, urease. The enzymes of the deiminase pathway (II) are as follows: 6, arginine deiminase; 7, ornithine carbamoyltransferase; 8, carbamate kinase. Glutamate semialdehyde is spontaneously converted to pyrroline 5-carboxylate, the more-stable cyclic form of glutamate semialdehyde. The last step in the arginase degradative pathway and proline degradation was reported to be catalyzed by different pyrroIine-5-carboxylate dehydrogenase isozymes in B. subtilis ( 23 ). However, the bacterial strain used in these studies ( 23 ) was subsequently found to be B. lichentformis ( 45 ).
Histidine degradative pathways. Pathway I is found in enteric bacteria and B. subtilis, while pathway II is present in pseudomonads and S. coelicolor. The enzymes are as follows: 1, histidase (hutH); 2, urocanase (hutU); 3, imida-zolonepropionate hydrolase QiutI); 4, formiminoglutamic acid formiminohydrolase (hutG); 5, formiminoglutamic acid iminohydrolase (hutF); 6, formylglutamic acid amidohydro-lase (hutG).
Histidine degradative pathways. Pathway I is found in enteric bacteria and B. subtilis, while pathway II is present in pseudomonads and S. coelicolor. The enzymes are as follows: 1, histidase (hutH); 2, urocanase (hutU); 3, imida-zolonepropionate hydrolase QiutI); 4, formiminoglutamic acid formiminohydrolase (hutG); 5, formiminoglutamic acid iminohydrolase (hutF); 6, formylglutamic acid amidohydro-lase (hutG).
Genetic organization of the B. subtilis hut genes. The physical map of the hutPHU genes is taken from reference 54. Abbreviations: P, hut promoter region; hutP, hut regulatory gene; hutH, histidase structural gene; hutU, urocanase structural gene.
Genetic organization of the B. subtilis hut genes. The physical map of the hutPHU genes is taken from reference 54. Abbreviations: P, hut promoter region; hutP, hut regulatory gene; hutH, histidase structural gene; hutU, urocanase structural gene.
Compounds used as nitrogen sources by B. subtilis 168 a
Compounds used as nitrogen sources by B. subtilis 168 a