title: Stimulation of expression of a silica-induced protein (Sip) in Thermus thermophilus by supersaturated silicic acid.
abstract: 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 degrees C. At concentrations higher than the solubility of amorphous silica (400 to 700 ppm SiO(2)), 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 Fe(3+) 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.
authors.affiliation: Department of Genetic Resources Technology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. doi@agr.kyushu-u.ac.jp
authors.forename: Katsumi
authors.initials: K
authors.lastname: Doi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fujino
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
authors.forename: Ryouichi
authors.initials: R
authors.lastname: Kawatsu
authors.forename: Miki
authors.initials: M
authors.lastname: Tahara
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohshima
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okaue
authors.forename: Takushi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Satoru
authors.initials: S
authors.lastname: Iwai
authors.forename: Seiya
authors.initials: S
authors.lastname: Ogata
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D019015:Geologic Sediments / Q000382:microbiology*; D045482:Hot Springs; D007564:Japan; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D020543:Proteome / Q000032:analysis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012824:Silicic Acid / Q000378:metabolism*; D016963:Thermus thermophilus / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D020543:Proteome; D012824:Silicic Acid