A bacterial cell–cell communication signal with cross‐kingdom structural analogues

TLDR

Extracellular signals, such as the bacterial diffusible signal factor (DSF), are central to microbial cell–cell communication and, due to their structural similarity to the fungal farnesoic acid, represent a cross‑kingdom conserved mechanism that may impact ecological and economic processes. The study identified DSF as cis‑11‑methyl‑2‑dodecenoic acid, showed that the α,β‑unsaturated double bond is essential for activity, demonstrated DSF‑like signaling in several Mycobacterium species, and concluded that α,β‑unsaturated fatty acids constitute a new class of extracellular signals for bacterial and fungal communication.

Abstract

Summary Extracellular signals are the key components of microbial cell–cell communication systems. This report identified a diffusible signal factor (DSF), which regulates virulence in Xanthomonas campestris pv. campestris , as cis ‐11‐methyl‐2‐dodecenoic acid, an α,β unsaturated fatty acid. Analysis of DSF derivatives established the double bond at the α,β positions as the most important structural feature for DSF biological activity. A range of bacterial pathogens, including several Mycobacterium species, also displayed DSF‐like activity. Furthermore, DSF is structurally and functionally related to farnesoic acid (FA), which regulates morphological transition and virulence by Candida albicans , a fungal pathogen. Similar to FA, which is also an α,β unsaturated fatty acid, DSF inhibits the dimorphic transition of C. albicans at a physiologically relevant concentration. We conclude that α,β unsaturated fatty acids represent a new class of extracellular signals for bacterial and fungal cell–cell communications. As prokaryote–eukaryote interactions are ubiquitous, such cross‐kingdom conservation in cell–cell communication systems might have significant ecological and economic importance.