Recombinase aided amplification (RAA) combined with lateral flow strip (LFS) for rapid detection of geosmin or 2-methylisoborneol in cyanobacteria

The secondary metabolites of cyanobacteria, geosmin (GSM) and 2-methylisoborneol (2-MIB), cause unpleasant taste and odor in surface waters globally, leading to water quality deterioration and consumer complaints when the water is used as a drinking water source. Hence, a simple, rapid, and intuitive method for detecting geosmin and 2-MIB in water is essential for real-time monitoring of odorous substances and ensuring water quality. In this study, two independent methods combining recombinase-aided amplification (RAA) with lateral flow strips (LFS) were developed to detect geosmin- and 2-MIB-producing cyanobacteria. They are the first applications of RAA-LFS technology for the rapid detection of geosmin and 2-MIB. These methods target the geoA and mic genes, which encode geosmin and 2-MIB, respectively. The assay for geoA detection achieved a limit of detection of 38.4 copies/reaction when using plasmid as DNA templates, and 1.13 cells/ reaction when the genomic DNA of cyanobacterium was used as the template. For the mic assay, the limit of detection was 68.2 copies/reaction with plasmid templates, and 48 cells/reaction when a cyanobacterial strain was used as the template. Additionally, the RAA-LFS assays exhibited high specificity with no cross-reactivity with non-geosmin- or non-2-MIB-producing cyanobacteria. Validation using 35 reservoir samples demonstrated the assays developed in this study are in 100 % concordance with the previously published and validated PCR assays. These findings suggest the developed assays offers distinct advantages with respect to its simplicity, rapidness, and sensitivity, positioning them as invaluable tools for on-site detection and monitoring of GSM and 2-MIB contamination. • First RAA-LFS assays detecting geosmin/2-MIB-producing cyanobacteria were developed. • The assays showed 100 % specificity with exceptional low limit of detections. • The assays for on-site detection can be completed within 25-min.