Using Spectral Flow Cytometry to Combat Harmful Algal Blooms in Drinking Water
Published December 2, 2024
Cyanobacteria, also known as blue-green algae, are microorganisms that use sunlight to make food. Under certain conditions, they can multiply rapidly to form harmful algal blooms (HABs). These blooms can produce toxins called cyanotoxins, which are potentially dangerous to both people and animals. When untreated, HABs can cause illnesses in people and domestic animals, disrupt aquatic ecosystems, and cause taste and odor issues in drinking water. There are several challenges to treating cyanobacteria in drinking water. For example, treatment options vary in how effective they are for different cyanotoxins. Understanding the growth patterns and species of cyanobacteria that make up the bloom, as well as the cyanotoxin properties, are important for effective management.
EPA researchers are developing new methods to evaluate the treatment of algae and cyanobacteria in drinking water systems. Through this research, scientists are optimizing the use of chemicals to reduce the presence of these organisms and protect the water ecology.
Hydrogen peroxide is a common chemical used to control algae growth entering water treatment plants, but it isn’t clear how it affects cyanobacteria cell physiology. In their study, EPA scientists exposed cyanobacteria to hydrogen peroxide and observed how it affected their cellular processes with the use of a technique called spectral flow cytometry. This technique allowed researchers to observe the light emitted by cyanobacteria—known as fluorescence emissions—during their metabolic processes. When cyanobacteria undergo photosynthesis, they absorb light, using most of it to generate energy while emitting the rest as light at specific wavelengths. Using a machine called a spectral flow cytometer, researchers measured light emissions from thousands of cyanobacteria cells in less than a minute. This allowed the researchers to see how cyanobacteria responded to hydrogen peroxide exposure.
Findings
When cyanobacteria were exposed to hydrogen peroxide, the research team observed two important changes in the cyanobacteria’s fluorescence emissions:
- An increase in green fluorescence, which could be from an imbalance in photosynthesis or the production of a different type of molecule.
- A decrease in red fluorescence, which is linked to photosynthesis.
The decrease in red fluorescence showed hydrogen peroxide’s disruption of cyanobacteria’s ability to photosynthesize, which was expected. In contrast, the increase in green fluorescence was a surprising discovery, since it has been unrelated to photosynthesis in previous research, and these findings are being further evaluated with a combination of laboratory and field studies. Despite uncertainty regarding the mechanisms behind these changes, the results demonstrate that examining the fluorescent characteristics of cyanobacteria can advance the understanding of cell physiology and the efficacy of water treatment chemicals by examining how chemicals disrupt their ability to photosynthesize. By understanding how the photosynthesis process is disrupted, the hope is that the amount of hydrogen peroxide added to water for treatment can be more refined and exact. Through these techniques and observations, this research provided a novel method to assess cyanobacteria responses to treatment chemicals like hydrogen peroxide.
What This Means for Water Treatment
By using spectral flow cytometry, EPA researchers can track how effectively hydrogen peroxide reduces cyanobacteria growth and refine treatment methods to improve water safety.
“What I think is exciting about these experiments is the measurements of changes in photosynthesis in the cyanobacteria after exposure to chemicals that indicates changes in metabolic activity,” EPA research biologist Robert Zucker explained. “Some of these changes in the fluorescence emissions from cyanobacteria have not previously been described in the scientific literature.”
By using advanced technologies like spectral flow cytometry, EPA researchers are uncovering new insights into how cyanobacteria interact with water treatment chemicals. This research can contribute to improving the safety of community drinking water and reducing the risk of HABs. As scientists continue to evaluate how chemicals affect cyanobacteria cell processes, the hope is that water treatment practices will become more efficient and adaptable, refining the amount of chemicals needed in treating water and ensuring cleaner and safer water.
This story was written by Virginia Vichi-Miller, Public Affairs Specialist for EPA’s Center for Public Health and Environmental Assessment (CPHEA) within the Office of Research and Development (ORD).