Skip to main content
. 2022 Dec 9;13:7608. doi: 10.1038/s41467-022-35311-4

Fig. 4. Cells produce bacteriocins (pyocins) as they move towards both clinical antibiotics and toxic supernatant collected from a competitor strain.

Fig. 4

A Our focal PAO1 strain is inhibited by cell-free supernatant of the soil-isolate Strain 7 but not of the clinical isolate PA14 (grey circles show measurements from 8 independent replicates; error bars show standard error). PAO1 moves towards the toxic supernatant from Strain 7 (β > 1, orange line; a two-sided binomial test at t = 17 h rejects the null hypothesis that trajectories are equally likely to be directed towards or away from supernatant (p < 0.0001, n = 911 cell trajectories)), but not towards the supernatant from the non-inhibitory PA14 (β ≈ 1, dark-green line; p = 0.669 at t = 17 h, n = 1333). Biological repeat shown in Fig. S19. B A representative PAO1 cell (see also Movie 5) undergoing chemotaxis towards ciprofloxacin gradually turns on pyocin expression (as visualised with an mNeonGreen reporter). The cell eventually undergoes lysis seen as a transient burst of DNA-labelling propidium iodine (shown in purple at t = 35 min). C Pyocin-expressing cells are more likely to move towards higher concentrations of ciprofloxacin and toxic Strain 7 supernatant (a two-sided binomial test rejects the null hypothesis that cells were equally likely to be moving towards or away from chemoattractant with p-values of p < 0.0001 and p = 0.004 respectively). This bias is absent in gradients of non-toxic PA14 supernatant (p = 0.711). Counts are pooled across two bio-replicates. D After 10 h in a ciprofloxacin gradient (CMAX = 10X MIC), many cells have undergone chemotaxis towards increasing ciprofloxacin concentrations and often express pyocins as they do so (quantified using mNeonGreen fusion). The proportion of cells expressing pyocins peaks near the middle of the microfluidic channel, where the ciprofloxacin gradient is relatively steep. E Similarly, many cells chemotaxing towards toxic Strain 7 supernatant also express pyocins. F Pyocin expression is also seen in gradients of non-toxic PA14 supernatant but cells do not bias their movement here. Source data are provided as a Source Data file.