Using Bacteria to Degrade Microcystin Toxins

Lake Erie harmful algal blooms (HABs) are dominated by microcystin (MC) toxin-producing cyanobacteria, including Microcystis species.  Of over 300 MC variants, Lake Erie HABs primarily release MC-LR, a cyclic and highly-stable heptapeptide which is a potent toxin to the liver and other organs.  Given concerns over human health and the high costs of water treatment, there is great interest in developing new methods to remove MC from contaminated waters.  We hypothesized that naturally-occurring Lake Erie bacteria have adapted to use MC-LR as an energy source.  As such, our lab isolated and characterized over 60 MC-degrading bacterial isolates that, when grown in various combinations, degraded MC-LR into non-toxic fragments.  In recent experiments, we have tested MC-LR degradation by less-complex groups of bacterial isolates (e.g., groups of 5, 4, 3, or 2 bacterial isolates) and have assessed bacterial member composition over time to correlate bacterial abundance with MC-LR degradation.  Liquid chromatography coupled to mass spectrometry (LC-MS) analysis of these cultures has confirmed MC-LR degradation by these less complex groups and identified several novel breakdown products, including previously unreported linear, tetrapeptide and tripeptide fragments, highlighting that our MC-degrading bacteria encode unique enzymes to degrade MC-LR.  Finally, in proof of principle experiments, we have demonstrated robust MC-LR degradation in biologically-active water filters (i.e.,biofilters), providing strong evidence that our bacteria could be used to treat drinking water.

Primary Presenter: Jason Huntley, University of Toledo College of Medicine and Life Sciences (jason.huntley@utoledo.edu)

Authors:

Jason Huntley, University of Toledo College of Medicine and Life Sciences  (Jason.Huntley@UToledo.edu)

Sharmila Thenuwara, University of Toledo  (sharmila.thenuwara@utoledo.edu)

Dragan Isaolovic, University of Toledo  (Dragan.Isailovic@utoledo.edu)