A molecular Redox Sensor from Streptomyces rimosus M4018 for Escherichia coli

Abstract

In order to enable microorganisms to manifest their intracellular oxygen levels we constructed a genetic sensor circuitry which converts signals impinging on the cellular redox balance into a reporter gene expression readout. Based on the newly found Streptomyces rimosus redox control system, consisting of Rex modulating Retinopathy of prematurity (ROP)-containing promoters in a NADH-dependent manner, we designed an Escherichia coli sensor transcription control system, which constitutes a Rex transactivator (REDOX) with the ability to bind and activate promoters. When oxygen levels were high and resulted in depleted NADH pools, Rex-specific target promoter (cydP1) driven from the expression of secreted (Green fluorscent protein, GFP) reporter gene was low as a consequence of increased Rex-ROP affinity. Conversely, at hypoxic conditions, it led to high intracellular NADH levels, strongly reduced Rex-ROP interaction and increased GFP expression in E. coli cells. The sensor capacity (oxygen levels) of redox system enabled monitoring of the population's metabolic state in vivo. Our research will not only help to understand the molecular mechanism of the Rex family but also foster progresses in biosensor development.