Metabolic Pathway Profiling in Intracellular and Extracellular Environments of Streptococcus thermophilus During pH-Controlled Batch Fermentations

Abstract

Elucidating the metabolite profiles during the growth of Streptococcus thermophilus is beneficial for understanding its growth characteristics. The changes in the intracellular and extracellular concentrations of carbohydrates, nucleotides, amino sugars, nucleoside sugars, fatty acids, and amino acids, as well as their metabolites over time, were investigated by metabolomics technology. Most metabolites of nucleotides were highly accumulated in the intracellular environment after the mid-exponential phase. Increases in the intracellular unsaturated fatty acids and N-acetyl-glucosamine and N-acetyl-muramoate recycling provided potential evidence that cell envelope remodeling occurred after the mid-exponential phase. At the later fermentation stages, potentially functional metabolite produced by glycine was highly accumulated in the intracellular environment. Additionally, potential toxic metabolites produced by phenylalanine and tyrosine could not be excreted into the extracellular environment in a timely basis. The accumulation of large amounts of these metabolites might be the primary cause of the overconsumption of amino acids and influence the growth of S. thermophilus.

Improved Sample Preparation for Untargeted Metabolomics Profiling of Escherichia coli

“…Bacteria possess the most vigorous enzyme systems and metabolic activity, the highest proportion of living cells, and the most stable physical and chemical properties during the mid-exponential phase ( 33 ). We first obtained growth curves of E. coli and determined that the mid-exponential phase was at an approximate optical density at 600 nm (OD 600 ) ≈ 0.35 (see Fig.…”

Comparative transcriptome analysis for the biosynthesis of antioxidant exopolysaccharide in Streptococcus thermophilusCS6

“…16 In S. thermophilus MN-ZLW-002, the intracellular concentrations of UDP-glucose, N-acetylglucosamine and N-acetyl-muramic acid significantly increased in the continuous fermentation (from mid-exponential to lateexponential to stationary phase). 27 Therefore, both environmental changes and fermentation time change can lead to the differences in intracellular sugar metabolism, mostly dependent on related gene regulation. 1 In CS6, maltose addition, soy peptone addition and initial pH did not influence the types of monosaccharide composition of EPSs, but influenced the molar ratios of monosaccharide composition of EPSs.…”

Time-course analysis of Streptococcus sanguinis after manganese depletion reveals changes in glycolytic and nucleic acid metabolites

“…Diverse mass spectrometry platforms such as LC–MS/MS, GC–MS and CE–MS with and without chromatography, and spectroscopy technologies such as NMR have enabled high-throughput discovery metabolomics in various biological systems, including bacteria, plants, and humans (Misra & Olivier, 2020 ). Recent studies have described the metabolomes of certain streptococci using various mass spectrometry methods: Streptococcus intermedius under various oxygen conditions (Fei et al, 2016 ); Streptococcus pneumoniae in chemically defined medium (Leonard et al, 2018 ); and Streptococcus thermophilus in pH-controlled batch fermentation (Liu et al, 2020 ; Qiao et al, 2019 ). To our knowledge, the metabolome of S. sanguinis has yet to be investigated.…”