Leveraging quorum sensing system for automatic coordination of Escherichia coli growth and lactic acid biosynthesis

Chang Ge,Hongkai Jia,Pingfang Tian,Shunqi Run

doi:10.1186/s13213-022-01663-x

Chang Ge, Hongkai Jia + Show 2 more

Open Access

https://doi.org/10.1186/s13213-022-01663-x

Copy DOI

Abstract

PurposeOverproduction of desired metabolites usually sacrifices cell growth. Here we report that quorum sensing (QS) can be exploited to coordinate cell growth and lactic acid production in Escherichia coli.MethodsWe engineered two QS strains: one strain overexpressing acyl-homoserine lactone (AHL) synthesis genes (“ON”), the other strain overexpressing both AHL synthesis and degradation gene (aiiA) (“ON to semi-OFF”). To clarify the impact of the QS system on lactic acid production, D-lactate dehydrogenase gene ldhA was deleted from the E. coli genome, and Enhanced Green Fluorescence Protein (eGFP) was used as the reporter.ResultsCompared to the “ON” strain, the “ON to semi-OFF” strain showed delayed log growth and decreased egfp expression at stationary phase. When egfp was replaced by ldhA for lactic acid production, compared to the wild-type strain, the “ON to semi-OFF” strain demonstrated 231.9% and 117.3% increase in D-lactic acid titer and space-time yield, respectively, while the “ON” strain demonstrated 83.6%, 31%, and 36% increase in growth rate, maximum OD600, and glucose consumption rate, respectively. Quantitative real-time PCR revealed that both ldhA and the genes for phosphotransferase system were up-regulated in ldhA-overexpressing “ON” strain compared to the strain only harboring QS system. Moreover, the “ON” strain showed considerable increase in glucose consumption after a short lag phase. Compared to the reference strain harboring only ldhA gene in vector, both the “ON” and “ON to semi-OFF” strains demonstrated synchronization between cell growth and D-lactic acid production.ConclusionsCollectively, QS can be leveraged to coordinate microbial growth and product formation.

Highlights

One primary mission of microbial metabolic engineering and synthetic biology is the high-level production of intended metabolites
Performance of Enhanced Green Fluorescence Protein (eGFP) Compared with Green Fluorescent Protein (GFP), eGFP manifests stronger fluorescence and has been widely used for protein labeling
We found that the lactic acid dehydrogenase (LdhA) specific activity of Q15 increased in the first 20 h and remarkably decreased, while that of Q12 increased in this first 32 h and slightly decreased (Fig. 3A)

Summary

Introduction

One primary mission of microbial metabolic engineering and synthetic biology is the high-level production of intended metabolites To this end, scientists have developed a set of strategies, including overexpression of key enzymes, deletion or attenuation of competing pathways (Jiang et al 2021; Wu et al, 2020a, b; Mazumdar et al 2010), management of ATP (Lan and Liao 2012), Ge et al Annals of Microbiology (2022) 72:4. AHL can pass through the cell membrane, and when AHL concentration reaches a threshold, cells start to orchestrate a series of biochemical events including bioluminescence, biofilm formation, and signal transduction. It is costly for a single cell to accomplish all the aforementioned events. Apart from LuxI-type QS system, other QS systems can coordinate cell growth and other events (Balestrino et al 2005; Sun et al 2016)

Objectives

Methods

Results

Discussion

Conclusion