Dataset Information

Comparative mRNA-Seq Analysis Reveals the Improved EPS Production Machinery in Streptococcus thermophilus ASCC 1275 During Optimized Milk Fermentation.

ABSTRACT: Exo-polysaccharide (EPS) produced by dairy starters plays critical roles in improving texture and functionalities of fermented dairy products. One of such high EPS producers, Streptococcus thermophilus ASCC 1275 (ST1275) was used as a model dairy strain to understand the stimulation of its EPS production under optimal milk fermentation conditions. The mRNA-seq analysis and targeted pathway analysis indicate that genes associated with lactose (milk sugar) catabolism, EPS assembly, proteolytic activity, and arginine/methionine/cysteine synthesis and transport in ST1275 were significantly up-regulated under the optimized conditions of pH 5.5, 40°C, or WPI supplementation compared to that of pH 6.5 and 37°C, respectively. This indicates that genes involved in above metabolisms cooperate together for improving EPS yield from ST1275. This study provides a global view map on potential targeted pathways and specific genes accounted for enhanced EPS production in Str. thermophilus and that could be modulated by fermentation conditions.

SUBMITTER: Wu Q

PROVIDER: S-EPMC5859087 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Comparative mRNA-Seq Analysis Reveals the Improved EPS Production Machinery in <i>Streptococcus thermophilus</i> ASCC 1275 During Optimized Milk Fermentation.

Wu Qinglong Q Shah Nagendra P NP

Frontiers in microbiology 20180313

Exo-polysaccharide (EPS) produced by dairy starters plays critical roles in improving texture and functionalities of fermented dairy products. One of such high EPS producers, <i>Streptococcus thermophilus</i> ASCC 1275 (ST1275) was used as a model dairy strain to understand the stimulation of its EPS production under optimal milk fermentation conditions. The mRNA-seq analysis and targeted pathway analysis indicate that genes associated with lactose (milk sugar) catabolism, EPS assembly, proteoly ...[more]

PMID: 29593689

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Project description:In a previous study, incorporation of high exopolysaccharide (EPS) producing dairy starter bacterium Streptococcus thermophilus ASCC 1275 was found to improve functionality of low fat mozzarella cheese and yogurt. This bacterium in its eps gene cluster has a unique pair of chain length determining genes, epsC- epsD, when compared to other sequenced S. thermophilus strains. Hence, the aim of this study was to understand the regulatory mechanism of EPS production in this bacterium using transcriptomic analysis to provide opportunities to improve the yield of EPS. As sugars are considered as one of the major determinants of EPS production, after preliminary screening, we selected three sugars, glucose, sucrose and lactose to identify the EPS producing mechanism of this bacterium in M17 medium. Complete RNA-seq analysis was performed using Illumina HiSeq 2000 sequencing system on S. thermophilus 1275 grown in three different sugars at two-time points, 5 h (log phase) and 10 h (stationary phase) to recognize the genes involved in sugar uptake, UDP-sugar formation, EPS assembly and export of EPS outside the bacterial cell. S. thermophilus 1275 was found to produce high amount of EPS (∼430 mg/L) in sucrose (1%) supplemented M17 medium when compared to other two sugars. Differential gene expression analysis revealed the involvement of phosphoenolpyruvate phosphotransferase system (PEP-PTS) for glucose and sucrose uptake, and lacS gene for lactose uptake. The pathways for the formation of UDP-glucose and UDP-galactose were highly upregulated in all the three sugars. In the presence of sucrose, eps1C1D2C2D were found to be highly expressed which refers to high EPS production. Protein homology study suggested the presence of Wzx/Wzy-dependent EPS synthesis and transport pathway in this bacterium. KEGG pathway and COG functional enrichment analysis were also performed to support the result. This is the first report providing the transcriptomic insights into the EPS production mechanism of a common dairy bacterium, S. thermophilus.

Project description:The high-gamma-amino butyric acid (GABA)-producing bacterium Levilactobacillus brevis strain NPS-QW 145, along with Streptococcus thermophilus (one of the two starter bacteria used to make yogurt for its proteolytic activity), enhances GABA production in milk. However, a mechanistic understanding of how Levilactobacillus brevis cooperates with S. thermophilus to stimulate GABA production has been lacking. Comparative peptidomic and metatranscriptomic analyses were carried out to unravel the casein and lactose utilization patterns during milk fermentation with the coculture. We found that particular peptides hydrolyzed by S. thermophilus ASCC1275 were transported and biodegraded with peptidase in Lb. brevis 145 to meet the growth needs of the latter. In addition, amino acid synthesis and metabolism in Lb. brevis 145 were activated to further support its growth. Glucose, as a result of lactose hydrolysis by S. thermophilus 1275, but not available lactose in milk, was metabolized as the main carbon source by Lb. brevis 145 for ATP production. In the stationary phase, under acidic conditions due to the accumulation of lactic acid produced by S. thermophilus 1275, the expression of genes involved in pyridoxal phosphate (coenzyme of glutamic acid decarboxylase) metabolism and glutamic acid decarboxylase (Gad) in Lb. brevis 145 was induced for GABA production.SIGNIFICANCE A huge market for GABA-rich milk as a dietary therapy for the management of hypertension is anticipated. The novelty of this work lies in applying peptide profiles supported by metatranscriptomics to elucidate (i) the pattern of casein hydrolysis by S. thermophilus 1275, (ii) the supply of peptides and glucose by S. thermophilus 1275 to Lb. brevis 145, (iii) the transportation of peptides in Lb. brevis and the degradation of peptides by this organism, which was reported to be nonproteolytic, and (iv) GABA production by Lb. brevis 145 under acidic conditions. Based on the widely reported contribution of lactic acid bacteria (LAB) and GABA to human health, the elucidation of interactions between the two groups of bacterial communities in the production of GABA-rich milk is important for promoting the development of functional dairy food and may provide new insight into the development of industrial GABA production.

Dataset Information

Comparative mRNA-Seq Analysis Reveals the Improved EPS Production Machinery in Streptococcus thermophilus ASCC 1275 During Optimized Milk Fermentation.

Publications

Comparative mRNA-Seq Analysis Reveals the Improved EPS Production Machinery in <i>Streptococcus thermophilus</i> ASCC 1275 During Optimized Milk Fermentation.

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