Measurements of noise in selected strains

Range Table - link
Organism Bacteria Escherichia coli
Reference Elowitz MB, Levine AJ, Siggia ED, Swain PS. Stochastic gene expression in a single cell. Science. 2002 Aug 16 297(5584):1183-6. p.1185 table 1PubMed ID12183631
Method "[Researchers] built strains of Escherichia coli, incorporating the distinguishable cyan (cfp) and yellow (yfp) alleles of green fluorescent protein in the chromosome. In each strain, the two reporter genes were controlled by identical promoters. To avoid systematic differences in copy number, [researchers] integrated the genes at loci equidistant from, and on opposite sides of, the origin of replication (fig. S1). The two fluorescent proteins exhibited statistically equivalent intensity distributions and thus displayed the necessary independence and equivalence to detect noise (ref 7)."
Comments "For measurement, cells were grown in LB medium and photographed through cfp and yfp fluorescence filter sets and in phase contrast (Fig. 2) (ref 7). A computerized image analysis system identified cells and quantified their mean fluorescent intensities. Both intrinsic and extrinsic noise could be determined from plots of CFP versus YFP fluorescence intensity in individual cells (Fig. 3A) (ref 7). The value of ?int indicates the mean relative difference in fluorescence intensity of the two reporter proteins in the same cell- for instance, if ?int = 0.25, then the two colors typically differ by about 25%. Because ?int and ?ext make orthogonal contributions to the total noise, ?tot, the three noise values satisfy the relation ?int^2 + ?ext^2 = ?tot^2 (refs 7, 8). Measurements of these variables for various strains and conditions are presented in Table 1." See notes beneath table
Entered by Uri M
ID 107859