A Portable Arsenic Sensor Integrating Bacillus megaterium with CMOS Technology

Bacteria innately monitor their environment by dynamically regulating gene expression to respond to fluctuating conditions. Through synthetic biology, we can harness this natural capability to design cell-based sensors. Bacillus megaterium, a soil bacterium, stands out due to its remarkable heavy metal tolerance and sporulation ability, making it an ideal candidate for heavy metal detection with low transportation costs. However, challenges persist: the synthetic biology toolkit for this strain is underdeveloped, and conventional whole-cell sensors necessitate specialized laboratory equipment to read the output. In our study, we have genetically modified B. megaterium for arsenic detection and established a detection threshold below the EPA's recommendation of 10 ppb for drinking water in both vegetative and spore forms. Additionally, we have integrated both engineered B. megaterium living cells and spores with a complementary metal-oxide-semiconductor (CMOS) chip, providing a proof-of-concept for field-deployable arsenic detection. We show that the limit of detection (LOD) of our integrated sensor is within the range to test arsenic levels in soil and food. As a proof of concept, this work paves the way for the deployment of our sensor in resource-limited settings, ensuring real-time arsenic detection in challenging environments.