Creation of a low cost, low light bioluminescence sensor for real time biological nitrate sensing in marine environments

ABSTRACT

The concentration of nitrate (NO³⁻) in Narragansett Bay has been shown to undergo considerable temporal and spatial variation. However, the dynamics of this flux has never been monitored on a fine-scale (<100 m, < 1 d) or in real-time. Whole-cell bio-reporters are promising candidates for low cost environmental sensing of bioavailable nutrients. Yet difficulties remain in creating sensors for long term deployment in the marine environment. This paper describes the creation and validation of a low-cost sensor using a self-bioluminescent strain of the cyanobacteria Synechococcus elongatus pcc 7942 for the direct measurement of bioavailable nitrate. Nitrate bioavailability was measured by monitoring light emission from a luxAB based promotor fusion to glnA using a light to frequency sensor and single board microcontroller. Sensor designs are presented in this manuscript with specific focus on storage, cell viability, and compatibility with the marine environment. Sensors were able to consistently assess nitrate standards as low as 1 ppm (16.3 μM). Using a wavelet denoising approach to reduce white noise and hardware noise, nitrate detection of standards as low as 0.037 ppm (0.65 μM) was achieved. Good sensitivity and low cost make these sensors ideal candidates for continuous monitoring of biological nitrates in estuarine systems.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biosensor
• nitrate
• cyanobacteria
• microcontroller
• low cost

Acknowledgements

The authors thank Dr. Jeffery Morgan for his expertise and assistance in the conceptualization, funding and review of this project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported in part by the Rhode Island Consortium for Coastal Ecology Assessment, Innovation and Modeling which is funded by the National Science Foundation under EPSCoR Research Infrastructure Improvement Award [grant number #OIA-1655221].