Fig. 3. GrowMiDE can maintain and enrich growth yield specialists through nutrient privatization.

A Fermentation pathways of L. lactis WT (black) and ∆ldhA (red) strains in mixed batch cultures or GrowMiDE enrichments. B Growth of L. lactis monocultures and cocultures (1:1 starting ratio) on CDM + 25 mM glucose (n = 3, biological replicates, error bars indicate SEM). C Frequencies of populations across transfers in mixed batch cultures of L. lactis strains on 50 mM glucose. Each transfer received a 1% inoculum into fresh CDM + 50 mM glucose, and CFUs for each strain were determined from the grown community at each transfer (n = 3, biological replicates, error bars indicate SEM). D Cell densities across transfers in GrowMiDE enrichments of L. lactis strains on 50 mM glucose. Initial mixed culture contained ~80% ∆ldhA as determined by CFUs/mL on CDM + Ery⁵ plates. At the end of each transfer, the DEs were disrupted in bulk by incubating with 1H,1H,2H,2H-perfluoro-1-octanol (PFO), diluted to an OD = 0.05 to achieve single-cell loading, and cells were re-packaged into DEs for the next transfer. (n = 3, technical replicates, error bars indicate SEM). CFUs for each strain were determined from the grown community at each transfer to determine relative cell densities, and the initial mixed culture contained ~80% ∆ldhA prior to splitting into batch or DE competition experiments. All L. lactis transfers were incubated for 48 h at 30 °C.