The relevance of carbon dioxide metabolism in Streptococcus thermophilus.
Streptococcus thermophilus is a major component of dairy starter cultures used for the manufacture of yoghurt and cheese. In this study, the CO(2) metabolism of S. thermophilus DSM 20617(T), grown in either a N(2) atmosphere or an enriched CO(2) atmosphere, was analysed using both genetic and proteomic approaches. Growth experiments performed in a chemically defined medium revealed that CO(2) depletion resulted in bacterial arginine, aspartate and uracil auxotrophy. Moreover, CO(2) depletion governed a significant change in cell morphology, and a high reduction in biomass production. A comparative proteomic analysis revealed that cells of S. thermophilus showed a different degree of energy status depending on the CO(2) availability. In agreement with proteomic data, cells grown under N(2) showed a significantly higher milk acidification rate compared with those grown in an enriched CO(2) atmosphere. Experiments carried out on S. thermophilus wild-type and its derivative mutant, which was inactivated in the phosphoenolpyruvate carboxylase and carbamoyl-phosphate synthase activities responsible for fixing CO(2) to organic molecules, suggested that the anaplerotic reactions governed by these enzymes have a central role in bacterial metabolism. Our results reveal the capnophilic nature of this micro-organism, underlining the essential role of CO(2) in S. thermophilus physiology, and suggesting potential applications in dairy fermentation processes.
Department of Food Science and Microbiology, Milan, Italy.
Stefania
S
Arioli
Istituto Sperimentale Italiano Lazzaro Spallanzani, sezione di Proteomica, Facoltà di Medicina Veterinaria, Milan, Italy.
Paola
P
Roncada
Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
Anna Maria
AM
Salzano
Department of Veterinary Pathology, Hygiene and Public Health, University of Milan, Milan, Italy.
Francesca
F
Deriu
IRCCS Policlinico San Matteo, Pavia, Italy.
Silvia
S
Corona
Department of Food Science and Microbiology, Milan, Italy.
Simone
S
Guglielmetti
Department of Veterinary Pathology, Hygiene and Public Health, University of Milan, Milan, Italy.
Luigi
L
Bonizzi
Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
Andrea
A
Scaloni
Department of Food Science and Microbiology, Milan, Italy.
Diego
D
Mora
D000818:Animals; D001120:Arginine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D005973:Glutamine / Q000096:biosynthesis; D007218:Industrial Microbiology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008892:Milk / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D048249:Streptococcus thermophilus / Q000378:metabolism* / Q000648:ultrastructure; D014508:Urea / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D020543:Proteome; D005973:Glutamine; D002245:Carbon Dioxide; D001224:Aspartic Acid; D010728:Phosphoenolpyruvate; D014508:Urea; D001120:Arginine; D007770:L-Lactate Dehydrogenase; D001616:beta-Galactosidase; D010730:Phosphoenolpyruvate Carboxylase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); D009584:Nitrogen