Abstract Title

Identification and Quantification of Degradation Products of Microcystins using High-Resolution UHPLC-Orbitrap-MS

Start Date

23-5-2022 5:45 PM

End Date

23-5-2022 7:00 PM

Abstract

Sharmila I. Thenuwara1, Jyotshana Gautam2, Samuel Simpson1, Johnna Birbeck3, Judy A. Westrick3, Jason F. Huntley2, Dragan Isailovic1

1Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH 43606 2Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH 43614

3Lumigen Instrumentation Center, Department of Chemistry, Wayne State University, Detroit, MI 48202

Microcystins (MCs) are heptapeptides produced by freshwater harmful algal blooms (HABs). Exposure to hepatotoxic MCs is a threat to humans and animals. Although conventional municipal water treatment processes can treat MC contaminated water, biodegradation of cyanotoxins using indigenous bacteria is cost-effective and environmentally friendly. We previously isolated and characterized five bacterial isolates from Lake Erie that degraded MC-LR into non-toxic fragments (Thees et al. 2018). Herein, degradation of MCs that are abundant in Lake Erie HABs, MC-LR and MC-RR, is investigated qualitatively and quantitatively using high-resolution LC-MS. UHPLC-Selected ion monitoring (SIM)-Orbitrap-MS analysis revealed two peaks at different retention times corresponding to m/z of a tetrapeptide degradation product. Fragmentation spectra of both peaks showed characteristic ADDA fragment with m/z 135.08. From the MS/MS spectrum, it was concluded that the peak with the shorter retention time than the substrate is linear tetrapeptide. These results indicate that the MC biodegradation mechanisms in Lake Erie bacteria may be distinct from those in other MC degrading bacteria. The enzymatic pathways and MC breakdown products are being investigated further.

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May 23rd, 5:45 PM May 23rd, 7:00 PM

Identification and Quantification of Degradation Products of Microcystins using High-Resolution UHPLC-Orbitrap-MS

Sharmila I. Thenuwara1, Jyotshana Gautam2, Samuel Simpson1, Johnna Birbeck3, Judy A. Westrick3, Jason F. Huntley2, Dragan Isailovic1

1Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH 43606 2Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH 43614

3Lumigen Instrumentation Center, Department of Chemistry, Wayne State University, Detroit, MI 48202

Microcystins (MCs) are heptapeptides produced by freshwater harmful algal blooms (HABs). Exposure to hepatotoxic MCs is a threat to humans and animals. Although conventional municipal water treatment processes can treat MC contaminated water, biodegradation of cyanotoxins using indigenous bacteria is cost-effective and environmentally friendly. We previously isolated and characterized five bacterial isolates from Lake Erie that degraded MC-LR into non-toxic fragments (Thees et al. 2018). Herein, degradation of MCs that are abundant in Lake Erie HABs, MC-LR and MC-RR, is investigated qualitatively and quantitatively using high-resolution LC-MS. UHPLC-Selected ion monitoring (SIM)-Orbitrap-MS analysis revealed two peaks at different retention times corresponding to m/z of a tetrapeptide degradation product. Fragmentation spectra of both peaks showed characteristic ADDA fragment with m/z 135.08. From the MS/MS spectrum, it was concluded that the peak with the shorter retention time than the substrate is linear tetrapeptide. These results indicate that the MC biodegradation mechanisms in Lake Erie bacteria may be distinct from those in other MC degrading bacteria. The enzymatic pathways and MC breakdown products are being investigated further.