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

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Title Aspartate Biosynthesis Is Essential for the Growth of
Streptococcus thermophilus in Milk, and Aspartate
Availability Modulates the Level of
Urease Activity.
 
Creator Arioli, S.
Monnet, C.
Prakash, M. Halami
 
Subject 02 Bacteriology
 
Description We investigated the carbon dioxide metabolism of Streptococcus thermophilus, evaluating the phenotype of
a phosphoenolpyruvate carboxylase-negative mutant obtained by replacement of a functional ppc gene with a
deleted and inactive version, �ppc. The growth of the mutant was compared to that of the parent strain in a
chemically defined medium and in milk, supplemented or not with L-aspartic acid, the final product of the
metabolic pathway governed by phosphoenolpyruvate carboxylase. It was concluded that aspartate present in
milk is not sufficient for the growth of S. thermophilus. As a consequence, phosphoenolpyruvate carboxylase
activity was considered fundamental for the biosynthesis of L-aspartic acid in S. thermophilus metabolism. This
enzymatic activity is therefore essential for growth of S. thermophilus in milk even if S. thermophilus was
cultured in association with proteinase-positive Lactobacillus delbrueckii subsp. bulgaricus. It was furthermore
observed that the supplementation of milk with aspartate significantly affected the level of urease activity.
Further experiments, carried out with a pureI-gusA recombinant strain, revealed that expression of the urease
operon was sensitive to the aspartate concentration in milk and to the cell availability of glutamate, glutamine,
and ammonium ions.
 
Date 2007
 
Type Article
PeerReviewed
 
Format pdf
 
Language en
 
Identifier http://ir.cftri.com/13235/1/Appl.%20Environ.%20Microbiol.-2007-Arioli-5789-96.pdf
Arioli, S. and Monnet, C. and Prakash, M. Halami (2007) Aspartate Biosynthesis Is Essential for the Growth of Streptococcus thermophilus in Milk, and Aspartate Availability Modulates the Level of Urease Activity. Applied and Environmental Microbiology, 73 (18). pp. 5789-5796.