Using native Lake Erie bacteria and their enzymes for degradation/removal of microcystin toxins from water

Microcystin-LR (MC-LR) is one of the most toxic and common cyanotoxins released by freshwater harmful algal blooms (HABs). While conventional water treatment practices can reduce/remove MC-LR from drinking water, bioremediation (i.e., biofilters) has additional advantages of being cost-effective and environmentally friendly. We previously isolated Lake Erie bacteria that degraded MC-LR into non-toxic fragments but the MC-LR degradation enzymes remain unknown. As such, the goal of this study was to use genomic sequencing and transcriptomics to identify MC-LR degrading genes/enzymes for water treatment. First, whole genome sequencing was performed on five MC-LR degrading bacteria, designated as ‘Group N,’ to predict potential MC-LR degrading genes/enzymes. Next, Group N bacteria were grown in sterile-filtered lake water, with or without MC-LR, and samples were collected every 3-4 days for either transcriptomic (RNA sequencing) or mass spectrometry analyses (MC-LR quantitation and fragment analysis). Bioinformatic analysis of genome sequences identified potential amidohydrolase, dipeptidase, leucyl aminopeptidase, peptidase, serine hydrolase, metallopeptidase, and serine hydrolase enzymes that could cleave MC-LR. Mass spectrometry analysis confirmed that Group N bacteria degraded cyclic MC-LR into non-toxic linear and tetrapeptide fragments. Finally, transcriptomic analysis is currently underway to identify genes upregulated in MC-LR containing cultures (compared to cultures without MC-LR). Putative MC-LR degrading enzymes will be recombinantly expressed/purified and MC-LR degradation confirmed by in vitro assays. These studies have the potential to reveal new methods to efficiently, safely, and cost-effectively remove MC-LR from water sources.