title: A tightly regulated expression system for E. coli using supersaturated silicic acid.
abstract: OBJECTIVE
  To develop a new expression system regulated by a ferric uptake regulator in which silicic acid is used as an inducer.
  
  
  RESULTS
  Fur box (binding site for Fur) was substituted for the lac operator to regulate the expression of GFP with the lac promoter. Since the addition of supersaturated silicic acid invokes iron deficiency, supersaturated silicic acids were used as an inducer. GFP expression was dependent on silica concentration, and the expression level without silica was negligible. Basal expression level of this lac-Fur system was extremely low and, hence, lytic enzyme gene E from bacteriophage ϕX174 could be retained in this system. Furthermore, the expression of genes of interest was spontaneously initiated as the cell density increased and the costs of the inducer are considerably less than IPTG.
  
  
  CONCLUSIONS
  The combination of lac promoter and Ferric uptake repressor allowed the protein expression by supersaturated silicic acid as an inducer in an easy and cost-effective way.
authors.affiliation: Faculty of Art and Science, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fujino
authors.affiliation: Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Tanoue
authors.affiliation: Department of Chemistry, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Yokoyama
authors.affiliation: Institute of Genetic Resources, 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
mesh_terms: D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D012824:Silicic Acid / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D012824:Silicic Acid
keywords: Ferric uptake regulator; Gene expression; Iron; Silicic acid; Thermus thermophilus