Extracellular chemoreceptor of deca-brominated diphenyl ether and its engineering in the hydrophobic chassis cell for organics biosensing

Abstract

• Global gene expression analysis reveals a novel biorecognition receptor of PBDEs. • Chemoreceptor of PBDEs is an extracellular Cache domain-containing sensor protein. • Sensor protein is displayed on the cell membrane of a hydrophobic chassis cell. • Hydrophobic whole-cell biosensor provides a specific and sensitive response to PBDEs. • It provides a new approach for quality monitoring and toxicity assessing of organics. Polybrominated diphenyl ethers (PBDEs) belong to a group of persistent organic pollutants and pose a risk of causing adverse effects to human health and the environment. Detection and monitoring of these compounds therefore is of great interest and need for remediation and health risk assessment. However, no specific receptor protein can be used as a biorecognition element for the development of PBDE-detecting whole-cell biosensor until now. The lack of knowledge of PBDEs metabolic pathways of bacteria and of bacterial regulatory networks is the main limitation in the successful biosensor design. In this study, the global gene expression analysis of promoter activation as a consequence of deca-BDE exposure led to the finding of a novel sensory element, extracellular Cache domain-containing sensor protein Chr1_2466, for specific biorecognition of PBDEs. A genetically engineered hydrophobic chassis cell, Sphingobium xenophagum C1, expressing firefly luciferase in place of Chr1_2466 on the cell membrane served as a whole-cell biosensor for PBDEs detecting. This biosensor was highly specific for PBDEs and had minimal interference from their structural analogues polychlorinated biphenyls, diphenyl ether, phenol, metals, and inorganic ions. The extracellular luminescence intensity of the hydrophobic whole-cell biosensor showed a linear relationship (R 2 = 0.98) from 0.05 to 6.0 µM of deca-BDE with a detection limit of 0.01 µM and a cytotoxicity threshold of 6.25 µM. Compared to the hydrophilic strain as chassis cell, such hydrophobic biosensor significantly increased the bioavailability and detection sensitivity of PBDEs. It provides a new approach for quality monitoring and toxicity assessing of hydrophobic organics.