OligoPerfect Designer software (Invitrogen, Carlsbad, CA) was used to select primers sequences. Secondary structures and dimer formation were predicted using Oligo Analyzer 3.0 software (Integrated DNA Technologies, Coralville, IA). Primers were purchased from Sigma-Aldrich (St Louis, MO). Real time PCR was click here performed using an Applied Biosystems 7300 Real-Time PCR System. The tuf gene of
L. brevis, encoding elongation factor Tu, was used as internal control for the analysis of tyrDC and aguA1 genes expression, as previously described for Streptococcus thermophilus[41]. Standard curves for both the internal-control and target genes were obtained by amplifying serial dilutions (ratio, 1:10) of the target sequences. Additionally, data were normalized in function of the amount of total RNA, according to Torriani et al. [42]. The amplifications were carried out in 20 μl reactions, by adding 5 μl of 1:20 diluted selleck products cDNA, to a real-time PCR mix containing Power SYBR Green PCR Master Mix (Applied Biosystems, Foster City, CA), according to
the manufacturer’s instructions, and 100 nM of each primer. The tyrDC (EMBL accession number LVIS_2213) specific cDNA was amplified with the TDC_F (5′-TGAGAAGGGTGCCGATATTC-3′) forward and the TDC_R (5′-GCACCTTCCAACTTCCCATA-3′) reverse primers. The aguA1 (EMBL accession number LVIS_2208) specific cDNA was amplified with the AGUA1_F (5′-TCTTGAAAATGCGACAGACG-3′) forward RG7420 molecular weight and the AGUA1_R (5′-TCCAACGTAGCCTGAGCTTT-3′) reverse primers. The TUF_F (5′-AGGCGACGAAGAACAAGAAA-3′) forward and the TUF_R (5′-CGATACGACCAGAAGCAACA-3′) reverse primers were used to amplify the tuf (EMBL accession number LVIS_1389) specific cDNA. Thermal cycling was as follows: initial denaturing at 95°C for 5 min followed by 35 cycles at 95°C for 15 s and 60°C for 35 s. The amplicons’ lengths were 141 bp, 240 bp and 159 bp for the tyrDC, aguA1 and tuf genes respectively and their specificity
was checked by melting curve analysis. A threshold cycle value (CT) was determined with a base line settled automatically. The relative expression level of genes was calculated by the 2-∆∆ct method, Tau-protein kinase using unstressed, and unsupplemented with BA precursors, total RNA as calibrator. The relative expression of tyrDC and aguA1 during the other experimental conditions was quantified as n-fold differences with respect to the calibrator. Real-time PCRs were performed in duplicate for each sample of cDNA, including a negative control in each run. Data were expressed as the mean of three independent experiments. Confocal laser scanning microscope Samples from each gastric stress condition were analyzed by confocal laser scanning microscopy (model TCS-SP2-AOBS, Leica Microsystems GmbH, Wetzlar, Germany), after staining with SYTO9 and propidium iodide (LIVE/DEAD® BacLight™ bacterial viability kit, Molecular Probes, Inc. AA Leiden, The Netherlands) to differentiate the cells as a function of compromised membranes.