Suicidal chemotaxis in bacteria

Abstract

Bacteria commonly live in surface-associated communities where steep gradients of antibiotics and other chemical compounds can occur. While many bacterial species move on surfaces, we know surprisingly little about how such antibiotic gradients affect cell motility. Here, we study the behaviour of the opportunistic pathogen Pseudomonas aeruginosa in stable spatial gradients of several antibiotics by tracking thousands of cells in microfluidic devices as they form biofilms. Unexpectedly, these experiments reveal that bacteria use pili-based (‘twitching’) motility to navigate towards antibiotics. Our analyses suggest that this behaviour is driven by a general response to the effects of antibiotics on cells. Migrating bacteria reach antibiotic concentrations hundreds of times higher than their minimum inhibitory concentration within hours and remain highly motile. However, isolating cells - using fluid-walled microfluidic devices - reveals that these bacteria are terminal and unable to reproduce. Despite moving towards their death, migrating cells are capable of entering a suicidal program to release bacteriocins that kill other bacteria. This behaviour suggests that the cells are responding to antibiotics as if they come from a competing colony growing nearby, inducing them to invade and attack. As a result, clinical antibiotics have the potential to lure bacteria to their death.

Pseudomonas aeruginosasurface motility and invasion into competing communities enhances interspecies antagonism

“…In addition to the chemosensory response, S. aureus PSMs also trigger a “competition sensing” response whereby P. aeruginosa upregulates type VI secretion system and pyoverdine biosynthesis pathways [39]. Similarly, P. aeruginosa has been reported to utilize type IV pili-mediated motility to perform “suicidal chemotaxis” toward antibiotics [58]. The upregulation of these common interbacterial competition pathways supports a model where P. aeruginosa senses potential danger in the environment and responds with directional twitching, while simultaneously activating defense mechanisms to combat the “enemy”.…”

Staphylococcalsecreted cytotoxins are competition sensing signals forPseudomonas aeruginosa

“…While PSMs do not affect the P. aeruginosa membrane sufficiently to allow permeabilization, even transient envelope stress may induce T6SS assembly and firing. Interestingly, it has been recently reported that P. aeruginosa chemotaxis towards, instead of away from, antibiotics and releases bacteriocins before dying 54 . While PSMs did not reduce P. aeruginosa viability, we found induction of two pyocins in P. aeruginosa in response to both PSMs pulse-in and co-culture with S. aureus , potentially supporting a similar “suicidal chemotaxis” model.…”

The motility and chemosensory systems of Rhizobium leguminosarum, their role in symbiosis, and link to PTSNtr regulation

“…Four technical replicate images were taken along the length of the capillary, at the top surface of the capillary. The images were then processed through an image analysis pipeline (http://github.com/AroneyS/Capillary-tracking) based on (Oliveira et al, 2022). This pipeline produced individual tracks for each bacterium, calculating the overall swimming speed and the tumble rate.…”