The type IV pilus chemoreceptor PilJ controls chemotaxis of one bacterial species towards another

Abstract

Bacteria live in social communities, where the ability to sense and respond to interspecies and environmental signals is critical for survival. We previously showed the pathogen Pseudomonas aeruginosa detects secreted peptides from bacterial competitors and navigates through interspecies signal gradients using pilus-based motility. Yet, it was unknown whether P. aeruginosa utilizes a designated chemosensory system for this behavior. Here, we performed a systematic genetic analysis of a putative pilus chemosensory system, followed by high-speed live-imaging and single-cell tracking, to reveal behaviors of mutants that retain motility but are blind to interspecies signals. The enzymes predicted to methylate (PilK) and demethylate (ChpB) the putative pilus chemoreceptor, PilJ, are necessary for cells to control the direction of migration. While these findings implicate PilJ as a bona fide chemoreceptor, such function had yet to be experimentally defined, as full-length PilJ is essential for motility. Thus, we constructed systematic genetic modifications of PilJ and found that without the predicted ligand binding domains or predicted methylation sites, cells lose the ability to detect competitor gradients, despite retaining pilus-mediated motility. Chemotaxis trajectory analysis revealed that increased probability and size of P. aeruginosa pilus-mediated steps towards S. aureus peptides, versus steps away, determines motility bias in wild-type cells. However, PilJ mutants blind to interspecies signals take less frequent steps towards S. aureus or steps of equal size towards and away. Collectively, this work uncovers the chemosensory nature of PilJ, provides insight into how cell movements are biased during pilus-based chemotaxis, and identifies chemotactic interactions necessary for bacterial survival in polymicrobial communities, revealing putative pathways where therapeutic intervention might disrupt bacterial communication.

Interactions betweenPseudomonas aeruginosaand six opportunistic pathogens cover a broad spectrum from mutualism to antagonism

“…Especially, interactions between key pathogens like P. aeruginosa and Staphylococcus aureus have been extensively studied as these species often co-occur in patients (Hotterbeekx et al, 2017; Ibberson and Whiteley, 2020; Limoli and Hoffman, 2019; Nguyen and Oglesby-Sherrouse, 2016). Research focused on various aspects including molecular mechanisms of interactions (Armbruster et al, 2016; Limoli et al, 2019; Yarrington et al, 2024; Zarrella and Khare, 2022), variation in interactions between different strains and across environments (Bernardy et al, 2022; Niggli et al, 2021; Niggli and Kümmerli, 2020), the evolution of interactions (Niggli et al, 2023; Tognon et al, 2017) and the consequences of interactions for the host (Orazi and O’Toole, 2017; Radlinski et al, 2017; Rezzoagli et al, 2020). Interactions among other pathogens (e.g.…”