Stimulation of expression of a silica-induced protein (Sip) in Thermus thermophilus by supersaturated silicic acid.
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.
Doi
Katsumi
K
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
Fujino
Yasuhiro
Y
Inagaki
Fumio
F
Kawatsu
Ryouichi
R
Tahara
Miki
M
Ohshima
Toshihisa
T
Okaue
Yoshihiro
Y
Yokoyama
Takushi
T
Iwai
Satoru
S
Ogata
Seiya
S
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
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D020543:Proteome; D012824:Silicic Acid