Intracellular arsenic concentration governs the threshold of the switching mechanism of an aggregation-based whole-cell biosensor.

抄録

Arsenite [As(III)] is a toxic metalloid widely present in the environment, and the development of cost-effective and sensitive microbial biosensors for As(III) detection is crucial for environmental monitoring. In this study, we designed a novel whole-cell biosensor based on the LuxR protein, which aggregates in response to As(III), triggering a switch-off output. To enhance the sensitivity of the sensor, the super-repressor mutant ArsR_C34Y and LuxR were combined to suppress the expression of the As(III) efflux pump ArsB. This modification resulted in a pronounced shift toward the OFF-type response. By introducing GlpF (an As(III) importer) and ArsB in the system, we demonstrated that the key to enhancing sensor sensitivity is efficiently modulating intracellular As(III) levels. Our findings show that the threshold for OFF-type switching remains constant at approximately 50–80 ag per cell, regardless of external As(III) concentration. This study provides novel insights into the quantitative relationship between intracellular As(III) levels and sensor output, offering a useful platform for future As(III) monitoring applications.