Implementation of Combinatorial Genetic and Microenvironmental Engineering to Microbial-Based Field-Deployable Microbead Biosensors for Highly Sensitive and Remote Chemical Detection

Engineered Biosensors in an Encapsulated and Deployable System for Environmental Chemical Detection

The long-term exposure of low levels of the fungicide, 2-phenylphenol (2-PP), to the environment presents a hazard to human and aquatic health. The cost and difficulty in large-scale production limit the use of existing sensors to detect 2-PP for applications such as personal protection and persistent environmental monitoring of large areas. While advances have been made in using whole cells as biosensors for specific chemical detection, a whole-cell biosensor system with robust biocontainment for field deployment and a strong visual reporter for readouts in the deployed environment has yet to be realized. Here, engineered biosensors in an encapsulated and deployable system (eBEADS) were created to demonstrate a portable, no-power living sensor for detection of 2-PP in the environment. A whole-cell living sensor to detect 2-PP was developed in Escherichia coli by utilizing the 2-PP degradation pathway with an agenetic amplification circuit to produce a visual colorimetric output. To enable field deployment, a physical biocontainment system comprising polyacrylamide alginate beads was designed to encapsulate sensor strains, support long-term viability without supplemental nutrients, and allow permeability of the target analyte. Integration of materials and sensing strains has led to the development of a potential deployable end-to-end living sensor that, with the addition of an amplification circuit, has up to a 66-fold increase in β-galactosidase reporter output over non-amplified strains, responding to as little as 1 μM 2-PP while unencapsulated and 10 μM 2-PP while encapsulated. eBEADS enable sensitive and specific in-field detection of environmental perturbations and chemical threats without electronics.

Comprehensive Enhancement of Mechanical, Water-Repellent and Antimicrobial Properties of Regenerated Seaweed and Plant-Based Paper with Chitosan Coating

Regenerated papers made from discarded natural sources, such as seaweeds or non-wood plants, are viewed as promising eco-friendly alternatives relative to conventional wood-based paper. However, due to its limited mechanical strength and higher water absorption than compared to traditional wood paper, it often results in premature structural disintegration. In order to overcome this limitation, this research introduces an efficient and comprehensive strategy of coating seaweed and plant papers with varying concentrations and molecular weights of chitosan. Increased concentration and molecular weight resulted in a greater amount of chitosan deposition, while the highest molecular weight also shows increased dissolution of soluble components of the paper. Since plants and seaweeds contain high anionic polysaccharide contents, the cationic chitosan shows high binding affinity towards paper. The resulting chitosan-coated papers demonstrate significant enhancements in water repellency and mechanical properties. In addition, the chitosan-coated papers also show significant bacterial inhibition effects due to the natural anti-microbial activity of chitosan.

An enhanced fluorescence detection of a nitroaromatic compound using bacteria embedded in porous poly lactic-co-glycolic acid microbeads

The detection of explosive nitroaromatic compounds has caused worldwide concern for human safety. In this study, we introduce a fluorescent biosensor based on porous biocompatible microspheres loaded with a bioreporter for the detection of nitroaromatic compounds. Poly(lactic-co-glycolic acid) microbeads were designed as biosensors embedded with the bacterial bioreporters. The genetically engineered bacterial bioreporter can express a green fluorescent protein in response to nitroaromatic compounds (e.g., trinitrotoluene and dinitrotoluene). The modified surface structure in microbeads provides a large surface area, as well as easy penetration, and increases the number of attached bioreporters for enhanced fluorescent signals of biosensors. Moreover, the addition of the M13 bacteriophage in open porous microbeads significantly amplified the fluorescence signal for detection by the π-π interaction between peptides in the M13 bacteriophage and nitroaromatic compounds. The modification of the surface morphology, as well as the genetically engineered M13 phage, significantly amplifies the fluorescence signal, which makes the detection of explosives easier, and has great potential for the stand-off remote sensing of TNT buried in the field.

Genome-wide gene-deletion screening identifies mutations that significantly enhance explosives vapor detection by a microbial sensor

Genetically engineered microbial biosensors, capable of detecting traces of explosives residues above buried military ordnance and emitting an optical signal in response, may potentially serve for the standoff detection of buried landmines. A promising candidate for such an application is a previously reported Escherichia coli-based reporter strain that employs the yqjF gene promoter as its sensing element; however, for this sensor to be able to detect actual landmines reliably, it was necessary for its detection sensitivity and signal intensity to be enhanced. In this study, a high-throughput approach was employed to screen the effects of individual gene deletions on yqjF activation by 2,4-dinitrotoluene (DNT). Several genes were identified, the deletion of which elicited a significant enhancement of yqjF induction by DNT. The most promising of these mutations were introduced into the sensor strain, individually or in pairs, yielding a considerable increase in signal intensity and a lowering of the detection threshold. A strain harboring two of the identified mutations, ygdD and eutE, appears to be the most sensitive microbial biosensor currently described for the detection of traces of landmine explosives.