Modeling Quorum Sensing Dynamics and Interference on Escherichia coli.

Carlos E Torres-Cerna,J Alejandro Morales,Esteban A Hernandez-Vargas

doi:10.3389/fmicb.2019.01835

Carlos E Torres-Cerna, J Alejandro Morales + Show 1 more

Open Access

https://doi.org/10.3389/fmicb.2019.01835

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Abstract

Bacteria control the expression of specific genes by Quorum Sensing (QS). This works using small signaling molecules called Autoinducers (AIs), for example, the Autoinducer-2 (AI-2). In this work, we present a mathematical model that represents the AI-2 dynamics on Escherichia coli, which is linked to the cell growth and the lsr operon expression. The model is adjusted using experimental data. Our results suggest that the extracellular AI-2 activity level depends on the cell growth rate, and this activity depends on the cell exponential growth phase. The model was adapted to simulate the interference of QS mechanisms in a co-culture of two E. coli strains: a wild type strain and a knock out strain that detects AI-2 but does not produce it. Co-culture simulations unveiled two conditions to avoid the QS on the wild strain: when the knock out takes control of the growth medium and overcomes the wild strain, or when is pre-cultured to its mid-exponential phase and then added to the wild strain culture. Model simulations unveiled new insights about the interference of bacterial communication and offer new tools for QS control.

Highlights

Quorum sensing (QS) is a bacterial communication mechanism used to coordinate cooperative behaviors by producing, releasing, and sensing small signaling molecules called Autoinducers (AIs)
Parameter fitting was assessed using the experimental data in the work of Xavier and Bassler (2005a), from this work we can use the three variables that we consider important in the E. coli QS dynamics: the extracellular AI-2 activity, the lsr operon expression, and the cell growth
The extracellular AI-2 activity on E. coli was analyzed indirectly by measuring the bioluminescence produced by the reporter bacterium Vibrio harveyi (Bassler et al, 1993), the lsr operon expression was analyzed by measuring the β-galactosidase units (Koop et al, 1987), and the cell growth is measured by the optical density

Summary

Introduction

Quorum sensing (QS) is a bacterial communication mechanism used to coordinate cooperative behaviors by producing, releasing, and sensing small signaling molecules called Autoinducers (AIs). The QS mechanisms are classified according to the type of AIs, the two of most studied are: the Acyl-homoserine lactone and oligopeptides, produced by Gram-negative and Gram-positive bacteria, respectively (Novick and Geisinger, 2008; Rutherford and Bassler, 2012). These AIs are highly specific, each AI has a cognate receptor in a specific bacterium, and cannot be sensed by other types of bacteria. Despite AIs-2 are produced in the same way in all bacteria by the LuxS enzyme, the signal transduction

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