Biosensor concentration was calculated by first constructing the invariant images from F₁ and F₂ using Eq. A6 (as illustrated with Fig. 2), then calculating an image average. Numbers listed are equal weight averages of image averages over n cells. Units are micromoles/liter of fiber. The difference in expression of the two fusion variants, examined in the SW strain, was of moderate significance (P < 0.10).