Cronobacter Support
05-19-2009, 03:09 PM
1st International Conference on Cronobacter Poster Abstract 44
Elucidating the white phenotype in Cronboacter sakazakii
Yellow pigmentation is one of the physiological features that have been used as criteria for the identification of Cronobacter spp., although only 70-80% of its strains express this feature. Within a recent study, the carotenogenic nature of the pigment produced in a Cronobacter spp. strain was elucidated by molecular and chemical means but so far, nothing is known about the molecular basis of the white phenotype or regulatory elements possibly involved in the expression of the pigment. To gain insight in the pigment production of Cronobacter spp. on the genetic level, a random transposon mutant library of strain C. sakazakii Es5 was screened for diminished pigment production. In addition, eight white wild type (wt) strains of Cronobacter spp. were analyzed by PCR and Dot Blot for the presence of the seven known pigment operon genes. By screening the transposon library build up with 10000 mutants, 35 white mutants were found. Mutations identified included the genes crtE, crtX, crtY, crtI, and crtB of the carotenoid operon, general regulators, genes involved in the sugar pathway and precursors for carotenoids, genes associated with basic cellular processes and a large proportion of poorly characterized or uncharacterized genes. With respect to the eight white wt strains we demonstrated the absence of all genes of the pigment operon for Cs1.7, whereas the presence of all genes of the pigment operon was disclosed for the remaining seven white strains. Some of the mutants as well as the white wt strain Cs1.7 show that the absence of one or several genes of the pigment operon can lead to loss of pigment production. Our results also prove a crucial role of regulatory elements in the expression of the white phenotype of Cronobacter spp. Selected white mutants will now be further characterized by phenotypic means and their performance regarding persistence and fitness in view of environmental stress factors.
Sophia Johler, Roger Stephan and Angelika Lehner
Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zürich, CH-8057, Zürich,
Switzerland.
Elucidating the white phenotype in Cronboacter sakazakii
Yellow pigmentation is one of the physiological features that have been used as criteria for the identification of Cronobacter spp., although only 70-80% of its strains express this feature. Within a recent study, the carotenogenic nature of the pigment produced in a Cronobacter spp. strain was elucidated by molecular and chemical means but so far, nothing is known about the molecular basis of the white phenotype or regulatory elements possibly involved in the expression of the pigment. To gain insight in the pigment production of Cronobacter spp. on the genetic level, a random transposon mutant library of strain C. sakazakii Es5 was screened for diminished pigment production. In addition, eight white wild type (wt) strains of Cronobacter spp. were analyzed by PCR and Dot Blot for the presence of the seven known pigment operon genes. By screening the transposon library build up with 10000 mutants, 35 white mutants were found. Mutations identified included the genes crtE, crtX, crtY, crtI, and crtB of the carotenoid operon, general regulators, genes involved in the sugar pathway and precursors for carotenoids, genes associated with basic cellular processes and a large proportion of poorly characterized or uncharacterized genes. With respect to the eight white wt strains we demonstrated the absence of all genes of the pigment operon for Cs1.7, whereas the presence of all genes of the pigment operon was disclosed for the remaining seven white strains. Some of the mutants as well as the white wt strain Cs1.7 show that the absence of one or several genes of the pigment operon can lead to loss of pigment production. Our results also prove a crucial role of regulatory elements in the expression of the white phenotype of Cronobacter spp. Selected white mutants will now be further characterized by phenotypic means and their performance regarding persistence and fitness in view of environmental stress factors.
Sophia Johler, Roger Stephan and Angelika Lehner
Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zürich, CH-8057, Zürich,
Switzerland.