We observed the expression profile of the total mRNA of TTHB212 deletion mutant of Thermus thermophilus HB8 strain grown in a rich (TR) medium at 70°C compared with that of wild type. Keywords: cell type comparison Three wild-type and mutant T. thermophilus HB8 strains were each pre-cultured at 70°C 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 (2 ml) were inoculated into 1 liter of the same medium and then cultivated at 70°C. Cells were collected after 5 h for wild-type and 7 h for TTHB212 deletion mutant, respectively, and then crude RNA was extracted. In order to compare mRNA expression in the TTHB212 deletion mutant with that of wild type, the expression of each mRNA was analyzed on a GeneChip as described under Sample Description Sheet of each sample in this website.