Emergent robustness of bacterial quorum sensing in fluid flow

Abstract

Bacteria use intercellular signaling, or quorum sensing (QS), to share information and respond collectively to aspects of their surroundings. The autoinducers that carry this information are exposed to the external environment; consequently, they are affected by factors such as removal through fluid flow, a ubiquitous feature of bacterial habitats ranging from the gut and lungs to lakes and oceans. To understand how QS genetic architectures in cells promote appropriate population-level phenotypes throughout the bacterial life cycle requires knowledge of how these architectures determine the QS response in realistic spatiotemporally varying flow conditions. Here we develop and apply a general theory that identifies and quantifies the conditions required for QS activation in fluid flow by systematically linking cell- and population-level genetic and physical processes. We predict that when a subset of the population meets these conditions, cell-level positive feedback promotes a robust collective response by overcoming flow-induced autoinducer concentration gradients. By accounting for a dynamic flow in our theory, we predict that positive feedback in cells acts as a low-pass filter at the population level in oscillatory flow, allowing a population to respond only to changes in flow that occur over slow enough timescales. Our theory is readily extendable and provides a framework for assessing the functional roles of diverse QS network architectures in realistic flow conditions.

pH variation in medical implant biofilms: Causes, measurements, and its implications for antibiotic resistance

“…Similar gradients can also be seen in bacterial quorum sensing molecules, which are intercellular signaling molecules produced by bacteria (Dalwadi and Pearce, 2021). Since low pH regions are indicative of high concentrations of bacteria, it is expected that quorum sensing molecules produced by these bacteria will also be in relatively high concentrations within a biofilm (Dalwadi and Pearce, 2021).…”

Single‐cell/nanoparticle trajectories reveal two‐tier Lévy‐like interactions across bacterial swarms

“…Due to the close distance between nearby cells and their slow displacement in biofilms or dense cell suspensions, it is reasonable to think that the multicellular communication is mainly achieved by passive diffusion of autoinducers. In fact, the external fluid flow would dilute local signal concentration, 47 resulting in a decrease in the QS efficiency, though a recent theoretical study proposed that slow and steady or oscillating flows can generate positive feedback that promotes QS 48 …”

Emergent spatiotemporal population dynamics with cell-length control of synthetic microbial consortia

“…For instance, we have ignored the mechanical interactions between cells and the extracellular matrix, which can impact the structures that emerge in biofilms [ 54 , 55 ]. We have also not included the impact of fluid flow at the colony boundaries, which can affect the concentration of QS signals in a colony [ 56 ]. However, such factors can be controlled in synthetic communities of E. coli growing in microfluidic devices [ 37 , 57 , 58 ], creating conditions close to the ones in our models.…”