Project description:Functional genomic analyses of exopolysaccharide-producing Streptococcus thermophilus ASCC 1275 in response to shifts in milk fermentation conditions
Project description:Purpose: High γ-aminobutyric acid (GABA)-producing Levilactobacillus brevis strain NPS-QW 145 along with Streptococcus thermophilus (one of the two starter bacteria used to make yogurt for its proteolytic activity) to enhance GABA production in milk. But a mechanistic understanding on how Levilactobacillus brevis cooperated with S. thermophilus to stimulate GABA production has been lacking. Method: Metatranscriptomic analyses combined with peptidomics were carried out to unravel the casein and lactose utilization patterns during milk fermentation with the co-culture. Results: We found particular peptides hydrolyzed by S. thermophilus 1275 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 also activated to further support its growth. Glucose, as a result of lactose hydrolysis by S. thermophilus 1275, but not available lactose in milk, was outcompeted by Lb. brevis 145 as a main carbon source for glycolysis to produce ATP.In the stationary phase, under the acidic condition due to accumulation of lactic acid produced by S. thermophilus 1275, genes expression involved in pyridoxal phosphate (coenzyme of glutamic acid decarboxylase) metabolism and glutamic acid decarboxylase (Gad) in Lb. brevis 145 were induced for GABA production.
Project description:Pastick2009 - Genome-scale metabolic network
of Streptococcus thermophilus (iMP429)
This model is described in the article:
Genome-scale model of
Streptococcus thermophilus LMG18311 for metabolic comparison of
lactic acid bacteria.
Pastink MI, Teusink B, Hols P,
Visser S, de Vos WM, Hugenholtz J.
Appl. Environ. Microbiol. 2009 Jun;
75(11): 3627-3633
Abstract:
In this report, we describe the amino acid metabolism and
amino acid dependency of the dairy bacterium Streptococcus
thermophilus LMG18311 and compare them with those of two other
characterized lactic acid bacteria, Lactococcus lactis and
Lactobacillus plantarum. Through the construction of a
genome-scale metabolic model of S. thermophilus, the metabolic
differences between the three bacteria were visualized by
direct projection on a metabolic map. The comparative analysis
revealed the minimal amino acid auxotrophy (only histidine and
methionine or cysteine) of S. thermophilus LMG18311 and the
broad variety of volatiles produced from amino acids compared
to the other two bacteria. It also revealed the limited number
of pyruvate branches, forcing this strain to use the
homofermentative metabolism for growth optimization. In
addition, some industrially relevant features could be
identified in S. thermophilus, such as the unique pathway for
acetaldehyde (yogurt flavor) production and the absence of a
complete pentose phosphate pathway.
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Project description:Transcriptional profiling of mutant Streptococcus thermophilus LMD-9 comR::lox72 (strain LF148) compared to mutant S. thermophilus LMD-9 DcomX (strain CB003) for the identification of the ComR regulon. Cells were grown in CDM medium supplemented with lactose 1% (CDML) and sampled at OD600 = 0.3~0.4 for mRNA extraction.
Project description:This study aimed to assess the effect of urease activity on the growth and energy metabolism of Streptococcus thermophilus in milk.
Project description:Central to genotoxic responses is their ability to sense highly specific signals to activate the appropriate repair response. We previously reported that the activation of the ASCC-ALKBH3 repair pathway is exquisitely specific to alkylation damage in human cells. Yet the mechanistic basis for the selectivity of this pathway was not immediately obvious. Here, we demonstrate that RNA but not DNA alkylation is the initiating signal for this process. Aberrantly methylated RNA is sufficient to recruit ASCC, while an RNA dealkylase suppresses ASCC recruitment during chemical alkylation. In turn, recruitment of ASCC during alkylation damage, which is mediated by the E3 ubiquitin ligase RNF113A, suppresses transcription and R-loop formation. We further show that alkylated pre-mRNA is sufficient to activate RNF113A E3 ligase in vitro in a manner dependent on its RNA binding Zn-finger domain. Together, our work identifies an unexpected role for RNA damage in eliciting a specific response to genotoxins.
Project description:Identification of the complete set of peptides produced by the htrA mutant strain of Streptococcus thermophilus LMD9 in the culture medium, based on three independent biological replicates.
