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Ca 2+ -Citrate Uptake and Metabolism in Lactobacillus casei ATCC 334

Authors :
Sergio H. Alarcón
Agata M. Pudlik
Juke S. Lolkema
Pablo Mortera
Christian Magni
Molecular Microbiology
Groningen Biomolecular Sciences and Biotechnology
Source :
Applied and environmental microbiology, 79(15), 4603-4612. AMER SOC MICROBIOLOGY, CONICET Digital (CONICET), Consejo Nacional de Investigaciones Científicas y Técnicas, instacron:CONICET
Publication Year :
2013
Publisher :
American Society for Microbiology, 2013.

Abstract

The putative citrate metabolic pathway in Lactobacillus casei ATCC 334 consists of the transporter CitH, a proton symporter of the citrate-divalent metal ion family of transporters CitMHS, citrate lyase, and the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Resting cells of Lactobacillus casei ATCC 334 metabolized citrate in complex with Ca 2+ and not as free citrate or the Mg 2+ -citrate complex, thereby identifying Ca 2+ -citrate as the substrate of the transporter CitH. The pathway was induced in the presence of Ca 2+ and citrate during growth and repressed by the presence of glucose and of galactose, most likely by a carbon catabolite repression mechanism. The end products of Ca 2+ -citrate metabolism by resting cells of Lb. casei were pyruvate, acetate, and acetoin, demonstrating the activity of the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Following pyruvate, the pathway splits into two branches. One branch is the classical citrate fermentation pathway producing acetoin by α-acetolactate synthase and α-acetolactate decarboxylase. The other branch yields acetate, for which the route is still obscure. Ca 2+ -citrate metabolism in a modified MRS medium lacking a carbohydrate did not significantly affect the growth characteristics, and generation of metabolic energy in the form of proton motive force (PMF) was not observed in resting cells. In contrast, carbohydrate/Ca 2+ -citrate cometabolism resulted in a higher biomass yield in batch culture. However, also with these cells, no generation of PMF was associated with Ca 2+ -citrate metabolism. It is concluded that citrate metabolism in Lb. casei is beneficial when it counteracts acidification by carbohydrate metabolism in later growth stages.

Details

ISSN :
10985336 and 00992240
Volume :
79
Database :
OpenAIRE
Journal :
Applied and Environmental Microbiology
Accession number :
edsair.doi.dedup.....93ad81b1bfd019a1fd270820772c9c2c
Full Text :
https://doi.org/10.1128/aem.00925-13