wild-type T. thermophilus HB8 strains were each pre-cultured at 70oC for 16 h in 3 ml of TR medium containing 0.8% polypeptone, 0.4% yeast extract, 0.2% NaCl, 0.4 mM CaCl2, and 0.4 mM MgCl2, which was adjusted to pH 7.2 with NaOH. The cells (0.3 ml) were inoculated into 0.15 liter of the same medium and then cultivated at 70oC. At the Abs600=0.8 (0min), cold medium was added and the temperature were shifted down to 45oC. Cells were collected at 0min and 30min after temperature shift, and then crude RNA was extracted.
Extracted molecule
total RNA
Extraction protocol
Cells were collected from 100 ml of the culture medium, and then crude RNA was extracted by the addition of 1.4 ml of a solution comprising 5 mM Tris-HCl, pH 7.5, 5 mM EDTA, 0.25% SDS, and 50% of water-saturated phenol. This mixture was incubated at 65｡C for 5 min, chilled on ice for 5 min, and then centrifuged at 4｡C. Then, 750 micro l of TRIZOL LS (Invitrogen, Carlsbad, CA) was added to 0.2 ml of the aqueous phase. After incubation for 5 min at room temperature, the RNA was extracted with 0.2 ml of chloroform. The extraction was repeated with 0.5 ml of chloroform, and the aqueous phase was precipitated with isopropanol. The pellet was dissolved in 0.2 ml of nuclease-free water, precipitated with ethanol, and then resuspended in 0.2 ml of water. The RNA was treated with DNase I (Ambion, Austin, TX) at 37｡C for 20 min in a 25-micro l reaction mixture. The reaction was terminated by the addition of 1 micro l of 0.5 M EDTA, followed by incubation at 70｡C for 5 min. Thereafter, the RNA was precipitated with ethanol in the presence of 1% glycogen and 1 M NH4OAc.
Label
biotin
Label protocol
cDNA was synthesized with SuperScript II (Invitrogen) reverse transcriptase in the presence of RNase inhibitor SUPERase (Ambion) and 6 base random primers (Invitrogen). The cDNA was fragmented with 1.2 units of DNase I (GE Healthcare Bio-Science Corp.) at 37｡C for 10 min, and after inactivation at 98｡C for 10 min, the cDNA fragments were labeled with GeneChip DNA Labeling Reagent (Affymetrix, Santa Clara, CA), using terminal transferase according to the manufacturer課ｪs instructions (Affymetrix).
Hybridization protocol
3'-terminal-labeled cDNA (2 micro g) was hybridized to a TTHB8401a520105F GeneChip (Affymetrix, Santa Clara, CA). The array was incubated for 16 h at 50｡C in a solution comprising 180 mM MES, pH 6.6, 40 mM EDTA, 0.02% Tween 20, 7% dimethyl sulfoxide, 20 micro g of herring sperm DNA (Promega), 0.1 mg of bovine serum albumin (BSA), the recommended amount of Eukaryotic Hybridization Control (Affymetrix), and Control Oligo B2 for the alignment signal (Affymetrix), and then the array was automatically washed and stained with streptavidin-phycoerythrin (Invitrogen) by using a GeneChip Fluidics Station, 450XP (Affymetrix).
Scan protocol
The Probe Array was scanned with a GeneChip Scanner 3000 (Affymetrix).
Description
gene expression data from log phase
Data processing
The image data was scaled to the target intensity by one-step Tukeyﾕs biweight algorithm using GeneChip Operating Software, version 1.1 (Affymetrix, Santa Clara, CA).
