A whole-cell hypersensitive biosensor for beta-lactams based on the AmpR-AmpC regulatory circuit from the Antarctic Pseudomonas sp. IB20.

Detecting antibiotic residues is vital to minimize their impact. Yet, existing methods are complex and costly. Biosensors offer an alternative. While many biosensors detect various antibiotics, specific ones for beta-lactams are lacking. To address this gap, a biosensor based on the AmpC beta-lactamase regulation system (ampR-ampC) from Pseudomonas sp. IB20, an Antarctic isolate, was developed in this study. The AmpR-AmpC system is well-conserved in the genus Pseudomonas and has been extensively studied for its involvement in peptidoglycan recycling and beta-lactam resistance. To create the biosensor, the ampC coding sequence was replaced with the mCherry fluorescent protein as a reporter, resulting in a transcriptional fusion. This construct was then inserted into Escherichia coli SN0301, a beta-lactam hypersensitive strain, generating a whole-cell biosensor. The biosensor demonstrated dose-dependent detection of penicillins, cephalosporins and carbapenems. However, the most interesting aspect of this work is the high sensitivity presented by the biosensor in the detection of carbapenems, as it was able to detect 8 pg/mL of meropenem and 40 pg/mL of imipenem and reach levels of 1-10 ng/mL for penicillins and cephalosporins. This makes the biosensor a powerful tool for the detection of beta-lactam antibiotics, specifically carbapenems, in different matrices.