A whole-cell nitrite sensor for aquaculture ponds

Background

Nitrite accumulates in intensive fish and shrimp ponds when the nitrogen cycle is disturbed, and is toxic to stock at low concentrations. Farmers test with chemical kits, which are accurate but slow and costly at scale. A biological sensor could be cheaper, but only if it reports quickly enough to change a decision.

Research question

Can an engineered bacterial sensor report nitrite in pond water at concentrations relevant to fish health, fast enough to be useful to a farmer at dawn?

Design process

• Human Practices first. Interviews with pond operators to learn when they test, what they do with a result, and what equipment they have at the pond.
• Design. A nitrite-responsive promoter driving a reporter, in a non-pathogenic chassis, with a containment strategy.
• Model. A production-and-loss model of reporter output to estimate time-to-signal at the target concentration, used to decide between fluorescent and colorimetric readouts.
• Test plan. Dose-response in buffer, then in filtered pond water, with controls for turbidity and temperature.

Findings

Not applicable for a sample project. A real project would report the dose-response data, the model comparison and the stakeholders' reaction to a prototype.

Safety

All wet-lab work in a project of this kind takes place in a supervised institutional laboratory under its biosafety rules.