Water quality is a critical factor for public health. Water is essential for drinking, cooking, and hygiene. This means that water testing and monitoring are essential to ensure that a community stays healthy. In fact, disease outbreaks have been repeatedly tied to contaminated water. This includes outbreaks of cholera, dysentery, typhoid, and many other bacterial and viral diseases. In addition, contaminated water can damage the environment and harm plant and animal ecosystems.
One important component of water quality testing involves the detection of coliform bacteria. This group of bacteria is gram-negative and can grow with or without oxygen. Coliform bacteria are ubiquitous in the environment, found in soil, surface water, and even on our skin. Importantly, these bacteria can also be found in fecal waste from humans and animals. This means that coliform bacteria can serve as indicator organisms, providing valuable information about potential contamination and the overall health of water sources. Their presence in water indicates pathways through which contamination can occur between water sources (such as rivers, lakes, or wells) and the water supply. Taken together, it’s no surprise that the Edvotek “Chromogenic Analysis of Water Contaminants” kit remains one of our best-selling experiments.
Types of Coliform Bacteria: One of the important features of the experiment is that it demonstrates how a scientist can differentiate between all coliform bacteria and those found in fecal matter.
- Total Coliforms: This broad category includes various bacteria, including coliforms. Their detection suggests possible contamination but does not necessarily indicate the presence of harmful pathogens.
- Fecal Coliforms: These bacteria specifically originate from the intestinal tracts of warm-blooded animals, including humans. Their presence indicates sewage or animal waste contamination.
- Escherichia coli (E. coli): A subset of fecal coliforms, E. coli is commonly found in the intestines of animals and humans. Its detection signals the potential entry of human or animal waste into the water supply.
During the experiment, students will perform three chromogenic, color-changing, assays to test for the presence of coliform and E.coli bacteria. As the bacteria grow and divide, they release specific enzymes into the nutrient medium. The first enzyme is present in all coliform bacteria (including E.coli). When present in the media, this enzyme cleaves the first indicator molecule, changing the color of the growth media from light yellow to blue-green. An E.coli-specific enzyme cleaves the second indicator molecule, producing a molecule with bright blue fluorescence when illuminated with long-wave UV light (i.e. a black light). To further confirm the presence of E.coli, the Indole test is performed. In the presence of E.coli, the addition of the Indole reagent will produce a distinctive red ring on top of the sample.
To learn more about this exciting experiment, or to examine this important assay in your lab, check out Edvotek experiment 951 – Chromogenic Analysis of Water Contaminants today! To learn more about water quality testing and the importance of clean water, check out some of our previous blog posts:
What’s in your water? Water Quality and Heavy Metal Testing
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