Non-Invasive Microbial Metabolic Activity Sensing at Single Cell Level by Perfusion of Calcein Acetoxymethyl Ester
Fig 7
Metabolic activity sensing of C. glutamicum wild type at intermittent nutrient limitation in minimal medium CGXII.
Bacterial cells were cultivated in minimal medium CGXII with 4% glucose (CGXII + 4% GLC) at pH 7 before an indicated shift to a depletion phase by switch of perfusion medium supply. (A) Reference cultivation under continuous supply of CGXII + 4% GLG. (B-D) After 4 h pre-cultivation, the microchambers were perfused with minimal medium (n = 10 colonies). (B) without iron chelator protocatechuate (PCA) (CGXII + 4% GLC—PCA, marked with violet boxes, n = 10 colonies), (C) without iron (CGXII + 4% GLC—iron, marked with black boxes, n = 10 colonies), and (D) with carbon limitation (CGXII—PCA, marked with red boxes, n = 10 colonies), respectively. For carbon and iron depletion conditions the medium was switched back to initial medium after 15 h. Microcolony images of every cultivation conditions are shown at different experimental time points. The mean fluorescence of the colony and apparent growth rate over time are shown in comparison to the extracellular mean fluorescence of the perfusion medium in the supply channel (10 μm fluid height), inside the cultivation chamber entrances (1 μm fluid height) and in the direct cell proximity (1 μm fluid height).