Fig. 5

Copper detection in the hydrogel plugs carrying yeast cells expressing pCu2, a ratiometric copper biosensor. A Plasmid pCu2 encoding copper inducible green fluorescent protein ymNeongreen and constitutively expressed red fluorescent protein ymScarletI. Labelled regions encode β-lactamase (bla), pUC19 replication origin (ori), copper-inducible promoter (pCUP1), constitutive promoter (pTEF2), and yeast terminators (ADH1t, CYC1t). B Inner cross-sections of the plugs incubated in 1.5 ml of water or media, with or without 10 µM Cu²⁺, with graphs marking the mean ratiometric signal. C Microcolonies at the edge and center of the plugs incubated in water with or without 10 µM Cu²⁺. D Microcolonies at the edge and center of plugs incubated in media with or without 10 µM Cu²⁺. E Surface of uncut plug incubated in media with 10 µM Cu²⁺, with graph showing mean ratiometric signal. F Microcolonies at the surface of the uncut plug after overnight incubation in medium with 10 µM Cu²⁺, with purple color denoting low Cu²⁺ concentration and yellow color high Cu²⁺ concentration. Scale bars: 1 mm in B and E, and 20 µm in C, D, and F