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.
Arioli
Stefania
S
Department of Food Science and Microbiology, Milan, Italy.
Roncada
Paola
P
Istituto Sperimentale Italiano Lazzaro Spallanzani, sezione di Proteomica, Facoltà di Medicina Veterinaria, Milan, Italy.
Salzano
Anna Maria
AM
Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
Deriu
Francesca
F
Department of Veterinary Pathology, Hygiene and Public Health, University of Milan, Milan, Italy.
Corona
Silvia
S
IRCCS Policlinico San Matteo, Pavia, Italy.
Guglielmetti
Simone
S
Department of Food Science and Microbiology, Milan, Italy.
Bonizzi
Luigi
L
Department of Veterinary Pathology, Hygiene and Public Health, University of Milan, Milan, Italy.
Scaloni
Andrea
A
Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
Mora
Diego
D
Department of Food Science and Microbiology, Milan, Italy.
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