Project Description

Background

Children and adults who drink water with high levels of manganese for an extended period of time experience issues with memory, attention, and motor skills. Infants may develop learning and behavior problems if they drink water with too much manganese in it. (MN Department of Health, 2019)

Problem

Manganese water contamination is a problem that cannot be easily corrected in some places. Common treatment options include oxidizing filters, ion exchange, aeration followed by filtration, and chemical oxidization followed by filtration(Connecticut Department of Public Health, n.d.). These are expensive solutions and not applicable to some communities. According to a representative of the Miami County Conservatory District, current diagnostic methods for water reservoirs require a sample sent to a lab for processing, which is also unrealistic for these communities.

Current Solutions

The current solutions for manganese contamination are usually either too expensive or unrealistic for other reasons. The aforementioned oxidizing filters, ion exchange systems, and aeration/oxidation combined with filtration can cost anywhere between $800 and $4,000 USD per household without taking into account costly maintenance that is required as often as every 6 months(Drinking Water Treatment-Oxidizing Filters, 2019).

Our Solution

Our goal is to engineer bacteria to sense the presence of manganese ions in water. In comparison to traditional methods, a biosensor would be far more accessible. In wild-type E. coli exists a system that the cell uses to mediate its internal manganese concentration. This system revolves around the Manganese Transport Regulator (MntR), which mediates the manganese importer and exporter depending on if it is bound to manganese. We used the mntP promoter, which is transcribed when MntR binds to manganese, and a riboswitch that forms a hairpin in low concentrations of manganese in conjunction with sfGFP for our biosensor. It has the potential to be dried on paper and may be used to diagnostically test a water sample in the field. A future direction of the project could include using the biosensor to control expression of phytochelatin to remove manganese ions from water.

Fig. 1. Schema of the function of the dual plasmid system in MG1655 WT E. coli. The IPTG-inducible 6xHIS-mntR negatively regulates pSB3K3-pmntP-rs-sfGFP sensor.