Fig. 1: Dead bacteria release a necrosignal. | Nature Communications

Fig. 1: Dead bacteria release a necrosignal.

From: Dead cells release a ‘necrosignal’ that activates antibiotic survival pathways in bacterial swarms

Fig. 1

a Graph showing distribution of the mean squared errors (MSE) between experimental and simulated killing curves of planktonic (green) and swarm (purple) cells shown in Supplementary Fig. 1a; 1 and 2 are simulations assuming homogeneous and heterogeneous populations, respectively (see “Methods”). The indicated p values were calculated from a two-tailed Wilcoxon rank sum test between the two types of populations. Median, solid black lines; quartiles, dashed black lines. bd Border-crossing assays that established the identity of the necrosignal. WT E. coli were inoculated in the left chamber in every case, whereas material applied to the right chamber is indicated below each plate. b None, no cells applied; Dead (Kan250), cells killed by Kan250; Pro K, cell extract supernatant from killed cells, treated with Proteinase K (see Supplementary Fig. 2b for supernatant alone); AS pel pellet fraction after treating supernatant with ammonium sulfate. Kan Kanamycin, Gen Gentamycin. c Gene deletions (Δ). All gene deletions were made with a Kan cassette, so the cells were pre-killed with Gentamycin (Gen50), and tested for swarming on Gen20. b2 serves as the control for these experiments. d Gene overexpression from ASKA library plasmids (p). These strains were pre-killed with Kan250. e Chart showing the species specificity of necrosignaling. Ec Escherichia coli, Se Salmonella enterica, Bs Bacillus subtilis, Pa Pseudomonas aeruginosa, Sm Serratia marcescens. Columns: bacterial species inoculated in the left chamber. Rows: bacterial species providing the dead cells applied on the right chamber, Maroon, SR+ response; Blue, SR− response. See “Methods” for the cell killing procedure and assay conditions, and Supplementary Fig. 2d for the raw data. f Swarming response to indicated Kan concentrations with increasing AcrA applied to the right chamber. The response was saturated at Kan70. Inset: minimum number of AcrA molecules estimated to be required for SR (calculated from moles of AcrA required per CFU/ml of swarm cells, n = 3) at the indicated Kan concentrations. The data (cyan dots) were fit to an exponential function (black line). Data are presented as mean values ± SD. Source data are provided as a Source Data file.

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