Antimicrobial screening of natural product extracts using a bioluminescent assay

We have developed a high throughput screening method for the discovery of new antimicrobial compounds, using a novel approach with recombinant bioluminescent bacterial strain Escherichia coli K-12/pTetLux. This recombinant strain can particularly be used to indicate compounds that affect microbial transcriptional and translational events [1]. The developed method improves the feasibility of using natural product extracts as a screening resource as the assay is less prone to interference from coloured or turbid samples. Compared to conventional antimicrobial testing, this biosensor-based method offers other important improvements such as simultaneous data on antimicrobial activity and mode of action and reduction of assay time from 24h to 2–3h. Results reported here include method validation and miniaturisation into 384-well plate format as well as implementation on 22 plant extracts from our in-house collection Based on the results, fractions of seven promising extracts that had been prepared by HPLC into 96 well-plates were further tested. The results show that the developed bioluminescent technology is well suitable for natural product screening and is sensitive enough to identify bioactive fractions.