Science Buddies: "Ask an Expert"

After reading the experiment "Worm Hunt: Isolating Soil Nematodes From Your Backyard" my questions are:

The E. Coli culture and nutrient agar I am ordering from Carolina Supply - will it be enough to have 18 soil samples ( 3 samples from 6 locations)?

In step 4 - it says to dampen the soil, while it is still in the baggies. How long can you keep the soil before you must use it? Will the nematodes die if I seal the baggies? I was wondering if I should collect soil samples before it rains and how long could the nematodes live in the baggies before I use the soil? Will the project have good results if I collect the soil have it has rained? Predictions of rain starting tomorrow and continuing for the next week have me concerned that the project may not work.

Hi,

This is a really great project!

https://www.sciencebuddies.org/science- ... s/Zoo_p045.

If you are ordering the agar plates suggested in the project, each package contains 10 agar plates.

http://www.carolina.com/p2p/endecaSearc ... Search.y=4

You could do two samples for each of 5 soil samples; with one package of plates, and I think this would be a nice project. Agar plates dry out with age and so make sure you are ready to do your experiment within a few days after they arrive. Leave them in the sealed package until you are ready to use them.

Don’t worry about the rain. Nematodes will survive nicely in the rain; the only problem is that you will get muddy when collecting soil samples immediately after a rain. Since this is a science project, you will want to keep all conditions the same, except for the soil samples. This means you should collect your samples shortly before you test them and add the samples to the agar plates with E. coli growing in the middle at the same time.

Nematodes are really small. Do you have a magnifying glass so you can look at them closely?

Donna Hardy

Thank you for your answer. I have a brock microscope low power and a maginfying glass. It has been raining here and flooded in some areas. What is a good depth I should dig at?

lytomich

Hi,

Your microscope and magnifying glass will be very helpful for this project. Nematodes are aerobic organisms so will be need to have access to air, so collect from the top surface of the soil if it is very wet. If you are comparing different types of soil, or different locations, then the depth of the each soil sample should be the same for each sample.


Donna Hardy

Would you suggest collecting soil by placing a tube in the ground to get a core or just scooping up the loose soil on the top?

Hi,

I would recommend scooping up some soil, perhaps with a plastic spoon, and transferring it into a plastic bag for transport back to the lab. If the soil is very hard, then a stronger digging implement may be needed, although with most wet soils, you should be able to get some dirt from the surface.

There has been research on the optimum soil depth of nematodes. Here’s one that reports the optimum moisture for the nematodes in sandy is between 5 and 9.5% moisture, and the nematodes will migrate to soil that contains optimum moisture.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2620435/

Here’s another report on nematodes associated with roots, and as expected, these nematodes are found at the same depth as the roots.

http://apsjournals.apsnet.org/doi/pdf/1 ... TO-96-0226

Since you are looking for bacteria-eating nematodes, these would likely be distributed throughout the soil.

Donna Hardy

Thank you.