Fig. 3: Electrochemical coating of bacterial surfaces.

a E. coli g(−) and S. epidermidis g(+) were labeled in a two-step procedure. The bacterial strains were first electrochemically decorated with azido-luminol derivative 1 for 15, 30 or 60 min, and the covalently anchored azido-tag was reacted with the DBCO-PEG₄-CR110 probe 5a by SPAAC for 1 h. b Optical and fluorescence images of E. coli and S. epidermis samples subjected to (i) only SPAAC (control) and (ii) eY-click and SPAAC. c Mean fluorescence intensity measured by flow cytometry for unmodified bacteria (E. coli or S. epidermidis), bacteria incubated with only DBCO-PEG₄-CR110 probe (only 5a), and conjugation experiments by eY-click with 1 for 15, 30 or 60 min followed by SPAAC with 5a. Data are shown as mean ± SD (standard deviation). Independent replicates were measured (n = 3). Statistical significance was assessed using one-way ANOVA tests with Dunnett’s multiple comparisons (means comparison) and is presented as 0.033>**P > 0.002> ***P. d Bacterial growth curves of 1-labeled E. coli samples after 1 h eY-click compared to untreated strains. Each sample was cultured (n = 3) and OD₆₀₀ was regularly measured. e SDS-PAGE electrophoresis on gels of non-fractionated proteins (total proteins), and proteins from membrane and cytosolic fractions after bacterial lysis and fractionation protocol applied to E. coli strains after 1 h electro-conjugation with 1 followed by 1 h SPAAC with 5a. Gels were colored by Coommassie Brilliant Blue (left) to confirm presence of all proteins in the fractions, and fluorescence detection at 490 nm (right) revealed fluorescent proteins in TP and MP lanes only, standing for a membrane electro-labeling.