Switches induced by quorum sensing in a model of enzyme-loaded microparticles

Abstract

4Quorum sensing refers to the ability of bacteria and other single-celled organisms to respond to 5 changes in cell density or number with population-wide changes in behaviour. Here, simulations were 6 performed to investigate quorum sensing in groups of diffusively-coupled enzyme microparticles using 7 a well characterised autocatalytic reaction which raises the pH of the medium: hydrolysis of urea by 8 urease. The enzyme urease is found in both plants and microorganisms and has been widely exploited 9 in engineering processes. We demonstrate how increases in group size can be used to achieve a 10 sigmoidal switch in pH at high enzyme loading, oscillations in pH at intermediate enzyme loading and 11 a bistable, hysteretic switch at low enzyme loading. Thus, quorum sensing can be exploited to obtain 12 different types of response in the same system, depending on the enzyme concentration. The 13 implications for microorganisms in colonies are discussed and the results could help in the design of 14 synthetic quorum sensing for biotechnology applications such as drug delivery. 15 16

Viewpoint: From Responsive to Adaptive and Interactive Materials and Materials Systems: A Roadmap

“…Other aspects, such as simplistic self‐replication (not graphically shown) have been discussed for self‐assembling systems, whereas quorum sensing has been addressed in bistable pH systems, chemical oscillators or in the DNA world . Collective behavior in light‐driven colloidal systems have been realized using competition between self‐propulsion and an attraction by osmotic and phoretic effects, allowing to synchronize motion in what was termed living crystals …”

Feedback and Communication in Active Hydrogel Spheres with pH Fronts: Facile Approaches to Grow Soft Hydrogel Structures

“…One prominent pH‐type CRN uses the urea‐urease driven pH feedback system that has been analyzed in homogeneous solution, or under confinement both experimentally and theoretically to exhibit feedback, front propagation, as well as bistable and oscillatory behavior. [ 46 , 47 , 48 , 49 , 50 ] Recently, we demonstrated more complex dual network systems (urea‐urease/ester‐esterase) in solution, [41] or under the confinement into layers [51] as a strategy towards new behavior in a stirred supernatant solution. In the context of this research, we hypothesized that fundamentally new and more complex behavior of CRNs may be accessible by exploiting the compartmentalization of antagonistic enzymatic networks (urea‐urease/ester‐esterase) into spatially organized hydrogel spheres, and by focusing on systems in non‐stirred condition so as to add reaction/diffusion components as additional system component to complexify the overall behavior.…”

Feedback and Communication in Active Hydrogel Spheres with pH Fronts: Facile Approaches to Grow Soft Hydrogel Structures

“…Such systems also benefit from their relatively simple analysis using pH. One prominent pH‐type CRN uses the urea‐urease driven pH feedback system that has been analyzed in homogeneous solution, or under confinement both experimentally and theoretically to exhibit feedback, front propagation, as well as bistable and oscillatory behavior [46–50] . Recently, we demonstrated more complex dual network systems (urea‐urease/ester‐esterase) in solution, [41] or under the confinement into layers [51] as a strategy towards new behavior in a stirred supernatant solution.…”