Do Gas Stations Affect the Soil Around Them?
To determine whether gas stations affect the soil around them by comparing the dominant types of soil microbes, as well as the pH level of soil samples, from the land around a typical gas station with those from land away from the gas station.
- 8-ounce (224-g) soil samples from the land around three gas stations
- 8-ounce (224-g) soil samples from an urban, suburban, and rural area distant from a gas station
- Distilled water
- 6 20-ml calibrated tubes with caps
- 6 sterile cotton swabs
- 6 petri dishes: tryptic soy agar with 5% sheep blood
- Masking tape
- Marking pen
- Gram's stain test materials (see Project 37)
- Sterile lab dish with depressions
- pH indicator
- 6 sterile plastic spatulas
Soil samples from the land around three different gas station locations will be tested to determine whether bacterial growth from these samples differs from the bacterial growth from soil samples taken from urban, suburban, and rural areas away from the gas stations, which will serve as the controls. Then, the pH levels of the soil samples from the different locations will be determined by per forming a pH indicator test.
- Place 1 ml of one gas station soil sample in a calibrated tube. Add 2 ml of distilled water and shake for 1 minute.
- Dip a sterile cotton swab into the tube and streak the swab onto a petri dish. Label the dish and incubate it for 48 hours.
- Remove the petri dish from the incubator. observe the bacterial growth, and make a Gram's stain (see steps 7 through 10 of Part I in Project 37) from the culture to determine whether the bacteria is gram-positive or gram-negative.
- Record and photograph your results. Repeat steps 1 through 3 for the remaining gas station soil samples and the control soil samples. Compare your results.
- Place a pea-sized portion of each soil sample into a separate depression of the lab dish to cover half the area of each depression, and label all.
- Add pH indicator drops to each depression so that you can see the color that forms, in order to be able to compare it to the pH color standards (be careful not to flood the depressions). Stir each depression with a sterile spatula.
- Tilt the lab dish to check the color of all the liquids, and record your pH findings. (The pH indicator will turn red in soil that is highly acidic and will turn blue to violet in soil that is highly alkaline.)
- Did the bacterial growth in the soil samples from the gas station sites differ from the bacterial growth of the control soil samples? Was the bacteria found to be gran1-positive or gram-negative?
- Which soil samples had the highest and lowest estimated pH levels?
- What is the overall effect that gas stations appear to have on the soil around them?
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