Using Indicator Bacteria to Monitor Public Water Supplies

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  • 0:07 The Benefits of Bacteria
  • 1:11 Indicators Warn Us
  • 2:39 Harmful Indicator Bacteria
  • 3:26 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

In this video lesson, you will learn about indicator bacteria. You will understand how and why they are used to test for water contamination despite the fact that they are harmless and naturally occurring in human and animal systems.

The Benefits of Bacteria

Bacteria sure do get a bad rap! Anti-bacterial hand cleaners, antibiotics, and other treatments are all designed to get rid of these microscopic organisms that come in all shapes and colors.

But actually, most bacteria are either harmless or beneficial to you! Just to name a few ways they help, beneficial bacteria keep harmful agents from getting through your skin to other organs, digest food in your stomach and intestines, help you absorb vitamins and minerals from your food, break down dangerous substances that get in your body, and fight disease.

E. coli is one such beneficial bacterium. E. coli is found in your colon, and it helps you absorb nutrients from your digested food that you can't take up on your own.

E. coli is just one of many indicator bacteria, which tell us if fecal contamination has occurred in a water supply. Indicator bacteria are for the most part harmless, but we test for them because if contamination has occurred, there is a good chance that bacteria that are harmful are present in the water supply as well.

Indicators Warn Us

There are many different types of indicator bacteria. We've already talked about E. coli, which lives in your colon. Others include the total coliforms, fecal coliforms, fecal streptococci, and enterococci.

These occur naturally in many animals and humans, and as mentioned before, they serve beneficial roles for us. Because they live in your gut, they often come out with fecal matter, so you can tell if fecal matter has gotten into the water supply by testing for these indicator bacteria.

However, fecal matter may also contain other harmful bacteria and pathogens. Typhoid fever, giardia, salmonella, and hepatitis A are all waterborne diseases, which means they travel through water bodies. These are harmful to both humans and animals and thrive in the same environment as the harmless indicator bacteria - your gut! So, if indicator bacteria are present, there's a good chance that other, more harmful bacteria are as well.

So, why not just test for the harmful bacteria? Indicator bacteria are used because they are more easily identifiable, tend to occur in larger numbers, and come from specific sources. However, just because indicator bacteria are present doesn't necessarily mean that harmful bacteria are as well. It just tells us that we need to look more closely at the contaminated water supply to identify possible harmful agents that may also be present, since they thrive in the same environments.

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