Aspartate Biosynthesis Is Essential for the Growth of Streptococcus thermophilus in Milk, and Aspartate Availability Modulates the Level of Urease Activity

• DOI: 10.1128/aem.00533-07
• Publication Date: 2007-07-28T00:54:04Z
• Authors: Stefania Arioli; Christophe Monnet; Simone Guglielmetti; Carlo Parini; Ivano De Noni; Johannes Hogenboom; Prakash M. Halami; Diego Mora
• Keywords: 0301 basic medicine; PHOSPHOENOLPYRUVATE CARBOXYLASE; CARBON DIOXIDE METABOLISM; 03 medical and health sciences; MILK; Animals; Streptococcus thermophilus; ASPARTATE; [SDV.EE]Life Sciences [q-bio]/Ecology, environment; bactérie; PPC GENE; Aspartic Acid; streptococcus thermophilus; Lactococcus-lactis; nitrogen-metabolism; acid; bacteria; sequence; proteinase; gene; CARBON DIOXIDE METABOLISM;PHOSPHOENOLPYRUVATE CARBOXYLASE;UREASE ACTIVITY;ASPARTATE;PPC GENE;MILK; Streptococcus; UREASE ACTIVITY; Gene Expression Regulation, Bacterial; Yogurt; lait; Urease; [SDV.EE] Life Sciences [q-bio]/Ecology, environment; Milk; Genes, Bacterial; Food Microbiology; Metabolic Networks and Pathways

We investigated the carbon dioxide metabolism of Streptococcus thermophilus, evaluating phenotype a phosphoenolpyruvate carboxylase-negative mutant obtained by replacement functional ppc gene with deleted and inactive version, Deltappc. The growth was compared to that parent strain in chemically defined medium milk, supplemented or not L-aspartic acid, final product metabolic pathway governed carboxylase. It concluded aspartate present milk is sufficient for S. thermophilus. As consequence, carboxylase activity considered fundamental biosynthesis acid thermophilus metabolism. This enzymatic therefore essential even if cultured association proteinase-positive Lactobacillus delbrueckii subsp. bulgaricus. furthermore observed supplementation significantly affected level urease activity. Further experiments, carried out p(ureI)-gusA recombinant strain, revealed expression operon sensitive concentration cell availability glutamate, glutamine, ammonium ions.