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[Preprint]. 2026 Apr 18:2026.02.13.705748. Originally published 2026 Feb 16. [Version 2] doi: 10.64898/2026.02.13.705748

Fig. 2.

Fig. 2

Fluorescent fusions of major chemoreceptors reveal extensive environment-dependent diversity in chemoreceptor composition across an isogenic bacterial population. (a) Schematic of the receptor protein quantification assay. The chemoreceptor Tar, which binds the amino acid L-aspartate, is fused at its native chromosomal locus to the fluorophore mCherry. The chemoreceptor Tsr, which binds the amino acid L-serine, is fused at its native chromosomal locus to the fluorophore mYFP. Imaging parameters were calibrated using a two-color fluorescent repressor-operator system (FROS) standard to equate the measured mCherry/YFP fluorescent intensity ratio to the true Tar/Tsr receptor abundance ratio (EDF 3). (b) Histogram of the Tar/Tsr chemoreceptor ratio measured with fluorescence microscopy for cells grown to OD = 0.45 in rich media, growth condition identical to the one used in figure 1b. The solid line represents the mean of four independent biological replicates, while shaded areas indicate the standard error of the mean across replicates. Inset: Correlation between Tar-mCherry and Tsr-mYFP expression levels. Each point represents a single cell, derived from four independent biological replicates. Tar and Tsr expression levels are strongly correlated (R2 = 0.70). (c) Relationship between the Tar/Tsr chemoreceptor ratio and OD for cells grown in rich (circles) and minimal (squares) media. Gray hollow points represent the mean of 40 technical replicates measured using a plate reader. Colored points represent the mean Tar/Tsr ratio measured via fluorescence microscopy from four (rich media) or three (minimal media) independent biological replicates for each OD. (d) Histograms of the Tar/Tsr chemoreceptor ratio measured via fluorescence microscopy for cells grown to different ODs in rich (solid line) or minimal (dashed line) media. Lines represent the mean distribution of all independent biological replicates, while shaded areas indicate the standard error of the mean across replicates. The color scheme is consistent with panel c.