Project description:Lcn972 is a non-modified bacteriocin that targets exclusively Lactococcus sp. Addition of Lcn972 inhibits cell wall biosynthesis at the septum by binding to the cell wall precursor lipid II. Resistance to Lcn972 develops upon selection with subinhibitory concentrations. The transcriptome of the highly resistant L. lactis D1 derived from the susceptible strain L. lactis MG1614 was compared. Fourteen genes were significantly up-regulated and 29 were down-regulated (expression change > 2-fold, p<0.001). Down-regulation was mostly found in sugar catabolic genes. Up-regulated genes included members of the cell envelope stress (CesR) regulon, the penicillin-binding protein pbpX and llmg2447, which may encode a putative extracytoplasmic function (ECF) anti-sigma factor located downstream of a non-functional ECF-sigX. Up-regulation of llmg2447 was linked to integration of IS981 that exchanged the -35 promoter region of llmg2447. Over-expression of llmg2447 resulted in highly Lcn972-resistant L. lactis transformants. The transcriptomes of Lactococcus lactis MG1614 susceptible to Lcn972 and L. lactis D1 resistant to Lcn972, grown under laboratory conditions, were compared using four biological replicates.
Project description:Lcn972 is a non-modified bacteriocin that targets exclusively Lactococcus sp. Addition of Lcn972 inhibits cell wall biosynthesis at the septum by binding to the cell wall precursor lipid II. Resistance to Lcn972 develops upon selection with subinhibitory concentrations. The transcriptome of the highly resistant L. lactis D1 derived from the susceptible strain L. lactis MG1614 was compared. Fourteen genes were significantly up-regulated and 29 were down-regulated (expression change > 2-fold, p<0.001). Down-regulation was mostly found in sugar catabolic genes. Up-regulated genes included members of the cell envelope stress (CesR) regulon, the penicillin-binding protein pbpX and llmg2447, which may encode a putative extracytoplasmic function (ECF) anti-sigma factor located downstream of a non-functional ECF-sigX. Up-regulation of llmg2447 was linked to integration of IS981 that exchanged the -35 promoter region of llmg2447. Over-expression of llmg2447 resulted in highly Lcn972-resistant L. lactis transformants.
Project description:The stringent response was defined in Lactococcus lactis through transcript profiling after the addition of a chemical inductor, the norvaline. Gene expression was measured in the exponential growth phase (reference sample) and at 1.6 h after norvaline addition. Four hundred and sixty one differentially expressed genes were identified and constituted the stringent response regulon. Keywords: stress response, time course Stringent response was imposed through norvaline addition during the growth of Lactococcus lactis IL1403 under controlled conditions (30 °C, pH 6.6, nitrogen atmosphere). Cell samples were harvested in exponential phase and 1.6 h after norvaline addition. Total RNA was extracted from these samples and radiolabelled cDNA were prepared and hybridized on nylon arrays. 2053 amplicons specific of Lactococcus lactis IL1403 genes were spotted twice on the array. The 2 time-points were analyzed simultaneously and 3 independent repetitions were performed.
Project description:For the first time in Lactococcus lactis, amino acid starvation response was characterized. The natural imposition of isoleucine starvation, by its consumption during growth, associated to transcript profiling, allowed defining exhaustively this stress stimulon. It consisted of a general induction of nitrogen metabolism (amino acid biosynthesis and transport, proteolytic system and proteases), a strong repression of genes encoding major physiological activities (translation, transcription, carbon metabolism, purine and pyrimidine biosynthesis and fatty acid metabolism) and the induction of unexpected cross responses to acid, osmotic and oxidative stresses. Keywords: stress response, time course Isoleucine starvation was imposed by the consumption of this amino acid during the growth of Lactococcus lactis IL1403 on ILV0.1 medium (CDM with ten-fold reduced concentrations of isoleucine, leucine and valine) and under controlled conditions (30 °C, pH 6.6, nitrogen atmosphere). Cell samples were harvested in exponential phase and after 30 min, 1.7 h and 3.5 h of isoleucine starvation. Total RNA was extracted from these samples and radiolabelled cDNA were prepared and hybridized on nylon arrays. 2053 amplicons specific of Lactococcus lactis IL1403 genes were spotted twice on the array. The 4 time-points were analyzed simultaneously and 3 independent repetitions were performed.
Project description:This SuperSeries is composed of the following subset Series: GSE23987: Transcriptomic profiles of six strains of Lactococcus lactis in ultrafiltration-cheese model GSE23990: Comparative genome hybridization profiles of six strains of Lactococcus lactis Refer to individual Series
Project description:Comparison of overall tRNA level in Lactococcus lactis affected by the growth rate and as a response to the overexpression of the membrane protein OpuA.