title: Histidine decarboxylaseless mutants of Lactobacillus 30a: isolation and growth properties.
abstract: Mutants of Lactobacillus 30a deficient in their ability to form an inducible histidine decarboxylase (EC 4.1.1.22) were selected by plating nitrosoguanidine-treated cultures on a medium containing histidine and methyl red. Wild-type organisms produce histamine, thus raising the pH and forming yellow colonies; mutant colonies remain red. In the presence of added histidine, decarboxylase-producing cultures grow more heavily than mutant cultures when the initial pH of the growth medium is low or when the lactic acid produced lowers the pH to growth-limiting values. Addition of the decarboxylation products, histamine and carbon dioxide, did not favor growth in crude medium.
mesh_terms: D001391:Azo Compounds; D002245:Carbon Dioxide / Q000096:biosynthesis; D002262:Carboxy-Lyases / Q000096:biosynthesis* / Q000378:metabolism; D003470:Culture Media; D005827:Genetics, Microbial; D006632:Histamine / Q000096:biosynthesis; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000096:biosynthesis; D007778:Lactobacillus / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D009153:Mutagens; D009154:Mutation; D009604:Nitrosoguanidines; D009952:Ornithine / Q000378:metabolism
chemical_list: D001391:Azo Compounds; D003470:Culture Media; D007773:Lactates; D009153:Mutagens; D009604:Nitrosoguanidines; D002245:Carbon Dioxide; D006639:Histidine; D006632:Histamine; D009952:Ornithine; D002262:Carboxy-Lyases