Stimulation of expression of a silica-induced protein (Sip) in Thermus thermophilus by supersaturated silicic acid

Katsumi Doi, Yasuhiro Fujino, Fumio Inagaki, Ryouichi Kawatsu, Miki Tahara, Toshihisa Ohshima, Yoshihiro Okaue, Takushi Yokoyama, Satoru Iwai, Seiya Ogata

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17 Citations (Scopus)


The effects of silicic acid on the growth of Thermus thermophilus TMY, an extreme thermophile isolated from a siliceous deposit formed from geothermal water at a geothermal power plant in Japan, were examined at 75°C. At concentrations higher than the solubility of amorphous silica (400 to 700 ppm SiO2), a silica-induced protein (Sip) was isolated from the cell envelope fraction of log-phase TMY cells grown in the presence of supersaturated silicic acid. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the molecular mass and pI of Sip to be about 35 kDa and 9.5, respectively. Induction of Sip expression occurred within 1 h after the addition of a supersaturating concentration of silicic acid to TM broth. Expression of Sip-like proteins was also observed in other thermophiles, including T. thermophilus HB8 and Thermus aquaticus YT-1. The amino acid sequence of Sip was similar to that of the predicted solute-binding protein of the Fe3+ ABC transporter in T. thermophilus HB8 (locus tag, TTHA1628; GenBank accession no. NC-006461; GeneID, 3169376). The sip gene (987-bp) product showed 87% identity with the TTHA1628 product and the presumed Fe 3+-binding protein of T. thermophilus HB27 (locus tag TTC1264; GenBank accession no. NC-005835; GeneID, 2774619). Within the genome, sip is situated as a component of the Fbp-type ABC transporter operon, which contains a palindromic structure immediately downstream of sip. This structure is conserved in other T. thermophilus genomes and may function as a terminator that causes definitive Sip expression in response to silica stress.

Original languageEnglish
Pages (from-to)2406-2413
Number of pages8
JournalApplied and environmental microbiology
Issue number8
Publication statusPublished - Apr 2009

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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