ArticleApplied and environmental microbiology2004
Characterization of a galactokinase-positive recombinant strain of Streptococcus thermophilus.
Article in Applied and environmental microbiology, 2004. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 12 papers.
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12 citing papers in PubMed, 32 citations in OpenAlex.
- Advances in Genetic Tools and Their Application inFoods (Basel, Switzerland) · 2023Review
- Effect of sugar transporter on galactose utilization inFrontiers in microbiology · 2023Article
- In Streptococcus thermophilus, Ammonia from Urea Hydrolysis Paradoxically Boosts Acidification and Reveals a New Regulatory Mechanism of Glycolysis.Microbiology spectrum · 2022Article
- Combination of Metabolomic and Proteomic Analysis Revealed Different Features amongFrontiers in microbiology · 2017Article
- New Insights into Various Production Characteristics of Streptococcus thermophilus Strains.International journal of molecular sciences · 2016Review
- Complete Genome Sequence of Streptococcus thermophilus SMQ-301, a Model Strain for Phage-Host Interactions.Genome announcements · 2015Article
- Preparation of low galactose yogurt using cultures of Gal(+) Streptococcus thermophilus in combination with Lactobacillus delbrueckii ssp. bulgaricus.Journal of food science and technology · 2014Article
- The cell envelope subtilisin-like proteinase is a virulence determinant for Streptococcus suis.BMC microbiology · 2010Article
- Role of galK and galM in galactose metabolism by Streptococcus thermophilus.Applied and environmental microbiology · 2008Article
- Molecular and biochemical analysis of the galactose phenotype of dairy Streptococcus thermophilus strains reveals four different fermentation profiles.Applied and environmental microbiology · 2005Article
- The doubly phosphorylated form of HPr, HPr(Ser~P)(His-P), is abundant in exponentially growing cells of Streptococcus thermophilus and phosphorylates the lactose transporter LacS as efficiently as HPr(His~P).Applied and environmental microbiology · 2005Article
- The relevance of genetic analysis to dairy bacteria: building upon our heritage.Microbial cell factories · 2004Article
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Authors and funding
6 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The lactic acid bacterium Streptococcus thermophilus is widely used by the dairy industry for its ability to transform lactose, the primary sugar found in milk, into lactic acid. Unlike the phylogenetically related species Streptococcus salivarius, S. thermophilus is unable to metabolize and grow on galactose and thus releases substantial amounts of this hexose into the external medium during growth on lactose. This metabolic property may result from the inability of S. thermophilus to synthesize galactokinase, an enzyme of the Leloir pathway that phosphorylates intracellular galactose to generate galactose-1-phosphate. In this work, we report the complementation of Gal(-) strain S. thermophilus SMQ-301 with S. salivarius galK, the gene that codes for galactokinase, and the characterization of recombinant strain SMQ-301K01. The recombinant strain, which was obtained by transformation of strain SMQ-301 with pTRKL2TK, a plasmid bearing S. salivarius galK, grew on galactose with a generation time of 55 min, which was almost double the generation time on lactose. Data confirmed that (i) the ability of SMQ-301K01 to grow on galactose resulted from the expression of S. salivarius galK and (ii) transcription of the plasmid-borne galK gene did not require GalR, a transcriptional regulator of the gal and lac operons, and did not interfere with the transcription of these operons. Unexpectedly, recombinant strain SMQ-301K01 still expelled galactose during growth on lactose, but only when the amount of the disaccharide in the medium exceeded 0.05%. Thus, unlike S. salivarius, the ability to metabolize galactose was not sufficient for S. thermophilus to simultaneously metabolize the glucose and galactose moieties of lactose. Nevertheless, during growth in milk and under time-temperature conditions that simulated those used to produce mozzarella cheese, the recombinant Gal(+) strain grew and produced acid more rapidly than the Gal(-) wild-type strain.
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