title: Construction of new cloning vectors that employ the phytoene synthase encoding gene for color screening of cloned DNA inserts in Thermus thermophilus.
abstract: Strains of Thermus thermophilus produce unique carotenoids called thermozeaxanthins and their colonies are light-yellow pigmented. Here, we developed a new cloning system allowing for the rapid and convenient detection of recombinants by color screening based on carotenoid production in T. thermophilus. We constructed two cloning vectors that overexpress the crtB gene encoding a phytoene synthase under the strong promoter of the slpA gene. Phytoene synthase is one of essential enzymes for the production of carotenoids. We also isolated a carotenoid-overproducing mutant that formed orange colonies. Because disruption of crtB in the carotenoid-overproducing mutant resulted in white colonies, we used the disruptant as a host strain. Whereas transformants carrying a new cloning vector, pTRK1-PRslpA-crtBcas, grew into unusual red-pigmented colonies probably because of the extreme accumulation of thermozeaxanthins, those carrying the vector with a foreign DNA inserts formed white colonies. Thus, recombinants can be detected easily by color screening (red/white screening) in T. thermophilus. This cloning system requires no additional chromogenic substrate in the medium. We also constructed a promoter-probe vector, pTRK1-crtBmcs-PP, employing the open reading frame of crtB with multiple cloning sites. Using this vector, a series of colony-color phenotypes is observed probably depending on promoter activities of foreign DNA inserts, which enables the rapid probing of promoters. These vectors are useful to simplify cloning procedures and to identify the promoters of different strengths in T. thermophilus.
authors.affiliation: Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka, Ikeda, Osaka 563-8577, Japan. a-fujita@aist.go.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fujita
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Misumi
authors.forename: Shinya
authors.initials: S
authors.lastname: Honda
authors.forename: Takaaki
authors.initials: T
authors.lastname: Sato
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Koyama
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003116:Color; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D005822:Genetic Vectors; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D016133:Polymerase Chain Reaction; D016963:Thermus thermophilus / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase
keywords: 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside; Carotenoid; Cloning vector; Color screening; Hyg; Km; MCS; ORF; Promoter-probe vector; S-layer; Surface layer; Thermus thermophilus; X-gal; base pair; bp; crtB; hygromycin; kanamycin; multiple cloning sites; open reading frame