Revolutionizing Water Quality Assessment: Chemical Pollutants Alter Bacterial Metabolism
USGS scientists have advanced methods to measure bacterial activity in environmental waters. Their research showed that when bacteria naturally in the water are exposed to substances like pharmaceuticals, herbicides, and antimicrobials, their normal functions are disrupted. This finding suggests that monitoring bacterial activity could provide early warnings about potential problems with water quality.
Risks associated with unknown or suspected chemical pollutants in our water systems are a concern. These pollutants can come from different sources such as farms, factories, or homes, and their impacts can vary based on the location and the seasons. Dominant features like rain, paved surfaces, and wastewater can lower water quality, but pinpointing the exact source causing these changes can be challenging. However, what is known is that a decrease in water quality affects microbes and can alter the composition of the bacterial community.
In general, polluted aquatic environments are nutrient-rich, and the bacteria are more active (higher bacterial respiratory and enzymatic activity). Scientists hypothesized that the impact of a swine farm where they were sampling would show increased bacterial metabolic activity, as indicated by esterase activity, compared to areas upstream or downstream from the farm. Monthly samples were taken over 17 months. The researchers noted that during 12 of those months, the bacterial esterase activity was lowest at the swine farm site. This raised an important question: “What unknown substances might be causing this reduced metabolic activity?” Traditional methods to identify such pollutants include sampling for nutrient levels, screening animal tissues for chemical concentrations, and applying analytical chemistry methods to measure the chemical mixtures. However, these methods are expensive and time-consuming.
To tackle this challenge, USGS scientists developed advanced flow cytometric (FCM) methods to measure bacterial metabolic activity. FCM is less expensive and delivers results quickly, typically within hours. While FCM has traditionally been used in aquatic microbiology for cell counts, size measurements, nucleic acid content determination, and cell viability, when combined with fluorescent staining FCM can help in monitoring, quantifying, and characterizing bacterial communities. This new approach allows scientists to explore opportunities to investigate cellular functions, helping to understand how bacteria respond to environmental change.
To test this new method, scientists exposed three bacterial species to five substances that can be detected in wastewater, including the herbicide atrazine, certain pharmaceuticals, and antimicrobial products. These substances significantly reduced the activity of bacterial esterase enzymes, which are essential for processes like cell division, metabolism, and breaking down certain harmful compounds. Atrazine (a highly soluble herbicide, and one of the most widely used herbicides in the United States), is frequently detected in agricultural streams; it showed the most significant impact on bacterial metabolism. This study demonstrated atrazine’s direct influence on microbes and their vulnerability to pollutants in the environment. Additionally, because many aquatic microbes cannot be cultured in a lab setting, FCM provides a way to compare how microbes function in clean versus potentially contaminated waters. This approach can also serve as a prescreening option before performing more extensive analyses of the occurrence and effects of suspected pollutants in watersheds.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), and the USGS Natural Resource Preservation Program.
USGS scientists have advanced methods to measure bacterial activity in environmental waters. Their research showed that when bacteria naturally in the water are exposed to substances like pharmaceuticals, herbicides, and antimicrobials, their normal functions are disrupted. This finding suggests that monitoring bacterial activity could provide early warnings about potential problems with water quality.
Risks associated with unknown or suspected chemical pollutants in our water systems are a concern. These pollutants can come from different sources such as farms, factories, or homes, and their impacts can vary based on the location and the seasons. Dominant features like rain, paved surfaces, and wastewater can lower water quality, but pinpointing the exact source causing these changes can be challenging. However, what is known is that a decrease in water quality affects microbes and can alter the composition of the bacterial community.
In general, polluted aquatic environments are nutrient-rich, and the bacteria are more active (higher bacterial respiratory and enzymatic activity). Scientists hypothesized that the impact of a swine farm where they were sampling would show increased bacterial metabolic activity, as indicated by esterase activity, compared to areas upstream or downstream from the farm. Monthly samples were taken over 17 months. The researchers noted that during 12 of those months, the bacterial esterase activity was lowest at the swine farm site. This raised an important question: “What unknown substances might be causing this reduced metabolic activity?” Traditional methods to identify such pollutants include sampling for nutrient levels, screening animal tissues for chemical concentrations, and applying analytical chemistry methods to measure the chemical mixtures. However, these methods are expensive and time-consuming.
To tackle this challenge, USGS scientists developed advanced flow cytometric (FCM) methods to measure bacterial metabolic activity. FCM is less expensive and delivers results quickly, typically within hours. While FCM has traditionally been used in aquatic microbiology for cell counts, size measurements, nucleic acid content determination, and cell viability, when combined with fluorescent staining FCM can help in monitoring, quantifying, and characterizing bacterial communities. This new approach allows scientists to explore opportunities to investigate cellular functions, helping to understand how bacteria respond to environmental change.
To test this new method, scientists exposed three bacterial species to five substances that can be detected in wastewater, including the herbicide atrazine, certain pharmaceuticals, and antimicrobial products. These substances significantly reduced the activity of bacterial esterase enzymes, which are essential for processes like cell division, metabolism, and breaking down certain harmful compounds. Atrazine (a highly soluble herbicide, and one of the most widely used herbicides in the United States), is frequently detected in agricultural streams; it showed the most significant impact on bacterial metabolism. This study demonstrated atrazine’s direct influence on microbes and their vulnerability to pollutants in the environment. Additionally, because many aquatic microbes cannot be cultured in a lab setting, FCM provides a way to compare how microbes function in clean versus potentially contaminated waters. This approach can also serve as a prescreening option before performing more extensive analyses of the occurrence and effects of suspected pollutants in watersheds.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), and the USGS Natural Resource Preservation Program.