Fecal Coliform Bacteria Tests

Summary

The video script details a scientific experiment to test for fecal coliform bacteria in various water samples using petri dishes with agar, a medium that supports bacterial growth. The experiment includes water from a pond in Riverside, California, fish tank water, tap water, and samples from the Santa Clara River, treated wastewater, bottled water, ocean water in Oxnard, reclaimed water from a pond, and a hiking trail in Whitney Canyon. Sterile pipettes are used to inoculate the agar with one milliliter of each water sample, which are then sealed and incubated. The results show that tap water, treated wastewater, and bottled water are negative for fecal coliform, while samples from the Santa Clara River, the reclaimed pond water, and the hiking trail in Whitney Canyon test positive, indicating the presence of bacteria from mammal feces. This serves as a cautionary tale about the importance of purifying or treating water from natural sources before consumption.

Takeaways

• 🧫 The purpose of the experiment is to check for fecal coliform bacteria in various water samples using petri dishes with agar.
• 🔬 Agar serves as a medium and food source for bacteria to grow and form colonies, with a special type turning pink to indicate fecal coliform bacteria.
• 📍 The water samples are sourced from different locations, including a pond in Riverside, California, a fish tank, tap water, and others.
• 🚿 A sterile pipette is used to take one milliliter of water from each sample to prevent contamination.
• 🚫 Petri dishes should be handled carefully to avoid leaving the lid off for too long, which can lead to airborne contamination.
• 🏷 Each petri dish is labeled according to its water source to keep track of the samples.
• 🛡️ Parafilm or a similar sealing material is used to seal the petri dishes, ensuring they remain closed to prevent contamination and pathogen exposure.
• 🔍 The results are observed by looking for the growth of colonies, specifically pink ones, which indicate the presence of fecal coliform bacteria.
• 🚰 Tap water showed no colonies, indicating the absence of fecal coliform bacteria, which is expected for treated water.
• 🐟 Fish tank water had bacterial growth but was negative for fecal coliform bacteria, suggesting the presence of beneficial bacteria for the tank's ecosystem.
• 🌊 Some water samples, like the one from the Santa Clara River, tested positive for fecal coliform bacteria, likely due to mammal feces runoff.
• ⛰️ Hiking trail water, such as from Whitney Canyon, tested positive for fecal coliform bacteria, emphasizing the need for water purification in outdoor activities.

Q & A

What is the purpose of using agar in the petri dishes?

Agar serves as a growth medium or food source for bacteria, allowing them to grow and form visible colonies on the petri dishes.

Why are fecal coliform bacteria specifically tested in water samples?

Fecal coliform bacteria are tested in water samples as indicators of possible sewage contamination and the presence of pathogens that could be harmful to human health.

What is the significance of the pink color of colonies in the testing process?

The pink color of colonies indicates the presence of fecal coliform bacteria. The special agar used is formulated to turn pink when these specific bacteria grow, facilitating their identification.

Why is it important to use sterile pipettes when transferring water samples to the petri dishes?

Using sterile pipettes prevents contamination of the samples with foreign bacteria or substances, ensuring the accuracy of the test results.

What is the role of parafilm in the experiment?

Parafilm is used to seal the petri dishes after inoculation to prevent any airborne contaminants from entering the dishes and to maintain the sterility and integrity of the experimental environment.

What does a negative result indicate in these tests?

A negative result indicates that no fecal coliform bacteria were detected in the sample, suggesting the water is free from contamination by mammal feces.

Why might tap water ideally show a negative result for fecal coliform presence?

Tap water should ideally show a negative result as it is treated and purified to be free from harmful bacteria, making it safe for consumption and domestic use.

Why is it mentioned that fish tank water normally contains good bacteria?

Fish tank water contains beneficial bacteria that help break down waste products in the aquarium, maintaining a balanced environment necessary for the health of the fish.

What could be the source of coliform bacteria in river water?

Coliform bacteria in river water could come from runoff containing animal feces, such as from dogs, or from wild animals like coyotes living near the river.

Why is it advised not to drink water directly from creeks or streams while hiking?

Drinking water directly from creeks or streams without treating it can be unsafe as it may contain coliform bacteria or other pathogens that can cause illness. It's advised to purify such water first by filtering, boiling, or using iodine drops.