RT Journal Article SR Electronic(1) A1 Arioli, Stefania A1 Roncada, Paola A1 Salzano, Anna Maria A1 Deriu, Francesca A1 Corona, Silvia A1 Guglielmetti, Simone A1 Bonizzi, Luigi A1 Scaloni, Andrea A1 Mora, DiegoYR 2009 T1 The relevance of carbon dioxide metabolism in Streptococcus thermophilus JF Microbiology, VO 155 IS 6 SP 1953 OP 1965 DO https://doi.org/10.1099/mic.0.024737-0 PB Microbiology Society, SN 1465-2080, AB Streptococcus thermophilus is a major component of dairy starter cultures used for the manufacture of yoghurt and cheese. In this study, the CO2 metabolism of S. thermophilus DSM 20617T, grown in either a N2 atmosphere or an enriched CO2 atmosphere, was analysed using both genetic and proteomic approaches. Growth experiments performed in a chemically defined medium revealed that CO2 depletion resulted in bacterial arginine, aspartate and uracil auxotrophy. Moreover, CO2 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 CO2 availability. In agreement with proteomic data, cells grown under N2 showed a significantly higher milk acidification rate compared with those grown in an enriched CO2 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 CO2 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 CO2 in S. thermophilus physiology, and suggesting potential applications in dairy fermentation processes., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.024737-0