Engineering a Rhamnose-Inducible System to Enhance the Extracellular Electron Transfer Ability of Shewanella Genus for Improved Cr(VI) Reduction

Abstract

Members of the Shewanella genus play important roles in bioenergy generation and environmental bioremediation, but their practical applications in engineered systems are still limited due to the lack of effective synthetic biology tools and parts such as promoters and expression systems. In this work, the rhaBAD promoter of Escherichia coli was introduced into various Shewanella species including S. oneidensis MR-1, S. decolorationis S12, and S. aquimarina SW-120 to enhance their extracellular pollutant transformation ability with Cr(VI) reduction as an example. The rhaBAD promoter had low leaky expression without L-rhamnose induction and exhibited a linear response to a wide concentration range. The inducer was nontoxic and could not be metabolizable by the Shewanella species. In addition, a unimodal induction of the rhaBAD promoter was found at the single-cell level. Applying this rhamnose-inducible system to the Shewanella species allowed for precise control on their extracellular electron transfer abilities to promote Cr(VI) transformation. The engineered strain induced by L-rhamnose reduced 98% Cr(VI) within 9 h, while only 59.1% Cr(VI) reduction was achieved by the control strain. Moreover, a 3-fold higher Cr(VI) reduction rate for the engineered strain induced by L-rhamnose confirms the improvement of its biotransformation ability. Our work provides an efficient regulation tool for engineering Shewanella species and may hopefully bring them a step further toward practical applications.

Respiration-induced biofilm formation as a driver for bacterial niche colonization

“…Oxygen-limitationinduced biofilm formation has been recently described in the plant-beneficial strain Bacillus amyloliquefaciens SQR9 and the underlying molecular mechanisms delineated [98], thereby paving the way towards the screening, selection, and modification of strains of agricultural interest. Proficient respiration-induced biofilm-forming Shewanella strains are also amenable to genetic manipulation and employment in microbial fuel cells or bioremediation [99,100], areas that are the focus of significant research efforts with this genus.…”

Composite modification of carbon fiber cathode with tree-like branched polypyrrole-microwires and polyaniline-nanorods for enhancing hexavalent chromium reduction

“…Several techniques have been well-developed for reducing Cr( vi ) to Cr( iii ) in wastewater, including photocatalytic, 6,7 biological, 8 chemical, 9 and electrochemical 10 reduction methods. The electrochemical reduction for Cr( vi ) detoxification has received extensive attention due to its easy operation, high efficiency, and limited sludge generation.…”

“…Since Cr(III) species with low solubility (pK sp = 30.2) are easily removed by precipitation, Cr(VI) reduction to Cr(III) has been regarded as an effective strategy for the treatment of Cr(VI)-contaminated wastewater. 5 Several techniques have been well-developed for reducing Cr(VI) to Cr(III) in wastewater, including photocatalytic, 6,7 biological, 8 chemical, 9 and electrochemical 10 reduction methods. The electrochemical reduction for Cr(VI) detoxification has received extensive attention due to its easy operation, high efficiency, and limited sludge generation.…”

A Thermally Regenerable Cationic MOF Adsorption Material for Sustainable and Selective Removal of Hexavalent Chromium from Water

“…Chromium has been extensively produced from electroplating, leather, painting, steel, and other industries, the treatment of point pollution could effectively control chromium emission. Various techniques have been applied to deal with Cr­(VI)-containing wastewater, including adsorption, , chemical precipitation, electrocoagulation, biological treatments, membrane filtration, reduction, , and photocatalysis . Among them, adsorption is a promising way for Cr­(VI) removal due to its simple operation, high removal rate, and low cost .…”