Physical communication pathways in bacteria: an extra layer to quorum sensing

Abstract

Bacterial communication is essential for survival, adaptation, and collective behavior. While chemical signaling, such as quorum sensing, has been extensively studied, physical cues play a significant role in bacterial interactions. This review explores the diverse range of physical stimuli, including mechanical forces, electromagnetic fields, temperature, acoustic vibrations, and light that bacteria may experience with their environment and within a community. By integrating these diverse communication pathways, bacteria can coordinate their activities and adapt to changing environmental conditions. Furthermore, we discuss how these physical stimuli modulate bacterial growth, lifestyle, motility, and biofilm formation. By understanding the underlying mechanisms, we can develop innovative strategies to combat bacterial infections and optimize industrial processes.

Keywords: Bacterial communication; Bacterial sensing; Bacterial signaling; Emerging properties; Environmental adaptation; Physical stimuli.

Fig. 1

Mechanosensing. Bacteria can sense mechanical cues, such as surface stiffness or liquid media viscosity, and respond actively through flagella and pili or passively through mechanosensitive channels. Mechanical strain in the bacterial membrane affects intracellular protein localization and divisome dynamics. Osmotic pressure, resulting from differences in solute concentrations with the environment, can also induce mechanical stress on the bacterial membrane

Fig. 2

Electric Stimuli and photosensing. Electric fields can influence bacterial ion transport and consequently, membrane potential, affecting key processes such as flagellar motility. Exposure to light can lead to oxidative stress, but light-sensitive proteins (rhodopsins, bacteriophytochromes, light-oxygen-voltage (LOV) domains, etc.) also regulate motility, gene expression, DNA repair, or synchronize activities with circadian rhythms (e. g., cryptochromes)

Fig. 3

Magnetic Sensing. Some bacteria biomineralize magnetosomes, membrane-enclosed magnetic nanoparticles whose alignment guides bacteria in magnetic fields and directs their motility in one dimension. Magnetic fields can also impact bacterial growth and DNA stability, affecting metabolism, gene expression, and morphology

Fig. 4

Thermosensing. Heat relaxes DNA supercoiling, exposing and activating heat-responsive genes, while heat shock proteins (e.g., RpoH) counteract protein damage. In contrast, cold increases supercoiling, condensing the DNA strand and suppressing gene expression to conserve energy and resources. It also induces the synthesis of c-di-GMP and promotes biofilm formation

Fig. 5

Mechanical coupling and bacterial collisions. A Swimming bacteria can sense the motion of distant swimmers by mechanical coupling through EPS production. B Collisions in bacterial swarms and direct physical contact cause cellular extrusion that can influence the assembly of the colonies in 3D and favour fruiting body formation

Fig. 6

Nanotube and nanowire communication. A Bacteria can establish cytoplasmic connection through nanotubes, lipid-based structures that might enable the transfer of nutrients, proteins, plasmids, and metabolites. B Similarly, nanowires facilitate the transport of electrons outside the cell to extracellular electron acceptors (other cells or mineral substrates)

Fig. 7

Long-range electrical communication. Electrical signaling coordinates metabolic exchange between interior and peripheral cells of biofilms. Propagating potassium waves alter the membrane potential, allowing inner cells undergoing nutrient depletion to communicate with peripheral cells. Potassium-based signaling can reach cells outside the biofilm, allowing interspecies communication

Fig. 8

Light and acoustic communication. A Bacteria emit electromagnetic radiation named “biophotons” that might be affected by the presence of stress and variation of metabolic activity in the cell. B Bacteria can sense and emit acoustic waves that stimulate their growth and alter intracellular ions and protein content. Due to mechanical resonance, sound signals can be amplified when bacteria communicate with their surrounding cells in community situations like biofilms