Regulating exopolysaccharide gene wcaF allows control of Escherichia coli biofilm formation

Jingyun Zhang,Chueh Loo Poh

doi:10.1038/s41598-018-31161-7

Abstract

While biofilms are known to cause problems in many areas of human health and the industry, biofilms are important in a number of engineering applications including wastewater management, bioremediation, and bioproduction of valuable chemicals. However, excessive biofilm growth remains a key challenge in the use of biofilms in these applications. As certain amount of biofilm growth is required for efficient use of biofilms, the ability to control and maintain biofilms at desired thickness is vital. To this end, we developed synthetic gene circuits to control E. coli MG1655 biofilm formation by using CRISPRi/dCas9 to regulate a gene (wcaF) involved in the synthesis of colanic acid (CA), a key polysaccharide in E. coli biofilm extracellular polymeric substance (EPS). We showed that the biofilm formation was inhibited when wcaF was repressed and the biofilms could be maintained at a different thickness over a period of time. We also demonstrated that it is also possible to control the biofilm thickness spatially by inhibiting wcaF gene using a genetic light switch. The results demonstrate that the approach has great potential as a new means to control and maintain biofilm thickness in biofilm related applications.

Highlights

Biofilms are widely found in nature and they are commonly formed by group of microorganisms sticking onto surfaces and forming slimy extracellular matrix
We first studied if biofilm formation could be inhibited when one of the colanic acid cluster genes was repressed by CRISPRi/dCas[9]
We have engineered E. coli MG1655 in which its wcaF gene within the genome can be regulated using aTc or light. wcaF was hypothesised to encode acetyltransferase which is involved in the synthesis of colanic acid[33]

Summary

Introduction

Biofilms are widely found in nature and they are commonly formed by group of microorganisms sticking onto surfaces and forming slimy extracellular matrix. Other biological methods include quorum quenching that interrupts autoinducer-mediated quorum sensing[20,30] and controlling the production of adhesive proteins such as csgA which could inhibit initial attachment of the bacteria[12]. These methods have been demonstrated to be able to either remove biofilm or prevent biofilm formation. Among these methods, targeting c-di-GMP and quorum quenching are most well studied. There still lack methods that could maintain the biofilm at a certain desired thickness

Objectives

Methods

Results

Conclusion