Module 4: Buoyancy

Description | Design | Construction | Characterisation | Modelling | Results | Conclusions

Description

The Buoyancy module is key to both the Degradation and the Aggregation systems. Buoyancy is required to position our bacteria in the water column, and also to enable them to buoy the plastic aggregates.

This module requires driving the expression of a gas vesicle gene cluster. Gas vesicles are formed within the cell, and are hollow spaces surrounded by a wall of hydrophobic protein. These gas vesicles are permeable to gases, which diffuse into the gas vesicles, increasing its partial pressure, thereby increasing buoyancy.

The Buoyancy system is subject to the control of a glucose-repressible promoter, PcstA (BBa_K118011). As a starvation promoter, production of gas vesicles will be limited in high cell nutrient environments, but increase as carbon sources become scarce. This gives us a gradient of activation which allows us to control the transcription of gas vesicle genes in different conditions. In our project, we expect this to occur as cells sink to greater depths in the ocean, thereby up regulating buoyancy as resources decrease, buoying our cells back to the targeted ocean surface.