Fig. 5: Spatial and temporal modes of amino acid cross-feeding in a synthetic E. coli consortium.

a Schematic of the experimental design. ΔmetA and ΔpheA are labeled with IPTG-inducible fluorescent reporters. The strains are initially cultured in the presence IPTG. At the denoted time, IPTG is removed and the media condition is altered. The maximum growth rate is inferred based on the rate of decay of the fluorescence signal. Relationship between distance and population-level doubling times of (b) ΔmetA or (c) ΔpheA. The dashed and solid lines represent presence and absence of methionine (M) and phenylalanine (F), respectively. Diamonds represent the model fits. Inset in c: the time of maximum ΔpheA growth rate in media lacking M and F. Horizontal lines denote a statistically significant difference (P < 0.05) based on one-tailed bootstrap hypothesis testing (Methods). *P < 0.05, **P < 0.01, and ***P < 0.001 (Supplementary Fig. 17). d Relationship between time and the average single-cell growth rates of ΔmetA and ΔpheA in a mixed community (solid line) or monoculture (dashed line) in media lacking M and F. Inset: fraction of cells with non-zero growth rates as a function of time. e Spearman’s correlation coefficient as a function of time between the fraction of the growth chamber occupied by the partner strain and the growth rate for individual cells (inset). The X symbol denotes correlations corresponding to P > 0.05. f Relationship between distance and the minimum doubling time in the presence of M and absence of F. ΔpheA exhibited two growth phases following the media switch (GP1 and GP2). Diamonds indicate model fits to the maximum growth rates in GP1. g Concentration of M or F divided by absorbance at 600 nm (OD600) in ΔpheA or ΔmetA conditioned media. Stars indicate the limit of detection for each measurement. 1× Amino acid fraction refers to 0.2 mM M and 0.4 mM F, respectively. The horizontal lines denote a statistically significant difference (P < 0.05) based on a two-sided t-test. *P < 0.05, **P < 0.01, and ***P < 0.001 (Supplementary Fig. 17). h Inferred interaction networks based on population-level maximum growth rates in spatially separated MISTiC experiments. The size of the node represents the maximum growth rate in the 25 μm (D₂₅) condition and is computed as (10 ln D₂₅⁻¹)². The edge widths represent the interaction strength defined as \({\it{D}}_{\it{d}} = 1 - {\it{D}}_{25}{\it{D}}_{250}^{ - 1}\) where D₂₅₀ denotes the maximum growth rate in the 250 μm condition. Source data are provided as a Source Data file.