Isolation and Identification of Microcystin-Degrading Bacteria in Lake Erie Source Waters and Drinking-Water Plant Sand Filters

Scientific Investigations Report 2023-5137
Prepared in cooperation with the U.S. Environmental Protection Agency, Great Lakes Restoration Initiative
By: , and 



The increasing prevalence of cyanobacterial harmful algal blooms and the toxins they produce is a global water-quality issue. In the Western Basin of Lake Erie, high microcystin concentrations have led to water-quality advisories, process adjustments for treating drinking water, and increased water-quality monitoring. Biodegradation is an environmentally friendly and cost-effective way to reduce concentrations of microcystins in drinking water; however, few studies have been done to determine biodegradation potential of bacteria indigenous to the Lake Erie watershed. As part of a cooperative program between the U.S. Geological Survey and the U.S. Environmental Protection Agency, this study aimed to identify naturally occurring microcystin-degrading bacteria in source waters and in the sand filters of drinking-water treatment plants in the Western Basin of Lake Erie. Biodegradation of microcystin-LR was found to occur in microcosms developed with three different Lake Erie-area sources—Lake Erie water, water from storage reservoirs supplied by inland streams, and water or solid medium from sand/anthracite filters at drinking-water plants. In microplates with microcystin-LR as the sole carbon source, 10 isolates exhibited cellular respiration and were, therefore, identified as promising microcystin biodegraders; 4 of those isolates subsequently were found to have potential to form biofilms. The 10 promising isolates along with 14 additional isolates from the microcosms were identified by 16S ribosomal RNA sequencing: 15 isolates were γ-proteobacteria, 6 isolates were β-proteobacteria, 1 isolate was an α-proteobacterium, 1 isolate was a flavobacterium in the phylum Bacteroidetes, and 1 isolate was in the phylum Actinobacteria. Isolates were screened for possession of the mlrA gene (found to encode for the protein responsible for cleaving the cyclic structure of microcystin), and results indicate that, for Lake Erie source waters and elsewhere, more work would be required to identify microcystin-biodegradation pathways and products and to confirm biodegradation rates in pure culture isolates.

Suggested Citation

Francy, D.S., Cicale, J.R., Stelzer, E.A., Reano, D.C., and Ecker, C.D., 2024, Isolation and identification of microcystin-degrading bacteria in Lake Erie source waters and drinking-water plant sand filters: U.S. Geological Survey Scientific Investigations Report 2023–5137, 23 p.,

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Purpose and Scope
  • Materials and Methods
  • Results
  • Discussion
  • Summary
  • References Cited
  • Appendix 1. Supplementary Tables
Publication type Report
Publication Subtype USGS Numbered Series
Title Isolation and identification of microcystin-degrading bacteria in Lake Erie source waters and drinking-water plant sand filters
Series title Scientific Investigations Report
Series number 2023-5137
DOI 10.3133/sir20235137
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Ohio-Kentucky-Indiana Water Science Center
Description Report: vii, 23 p.; Data Release
Country United States
Other Geospatial Lake Erie
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details