Ya Dig? A Look Into Soil Biodiversity and Why You Should Care

Here we are, one week out from our original sampling excursion outside our campus grocery store/Subway, and we are proud to report substantial microbial growth. The plated colonies have continued to grow in size (and grossness) over the past few days. The most growth remains on the plate that contains the highest concentration of soil sample (diluted 1000-fold), while the least amount of growth remains on the most diluted sample plate (diluted more than a million fold).

We now turn our focus on observations of biodiversity within our samples. After one week of incubation, we have witnessed the growth of many different types of bacterial and fungal colonies. These colonies vary in size, texture, and color. Some colonies have dark, discolored centers, while other remain uniform in color. Some are raised dramatically from the plate surface, and still others are as flat as pancakes. Some colony edges appear circular, while others stretch wildly across the plate. Every variance in appearance between colonies indicates a change in species, implying that our soil sample contained more types of organisms than could allow for peace of mind. The presence of a single fungal colony on our flourescent growth plate suggests a greater biodiversity among bacteria than fungi in the sample area. By applying some simple algebra, we estimated that there were 50,000 microbes per gram of soil at our sampling location.

You might be asking, "Why does soil biodiversity matter?" Well, it's really important - to say the least. Bacteria in the soil are responsible for the decomposition of organic matter. By breaking this matter down, they release nutrients into the soil that are vital for the production of the natural fertilizers that allow for agriculture. Basically, if we don't have any soil biodiversity, we have no food! You can find more information about the importance of soil microbes by clicking on the following link: http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/soil-biodiversity/agriculture-and-soil-biodiversity/en/

Come back next week for updated pictures and more dirt on dirt!
- Austin and Anne

Talk Dirty To Me: A Preliminary Snapshot of Our Soil Microbiology Study

If you can call yourself a Panther, you've definitely made a few visits to the BSC C-Store/Subway. So, what's actually going on under this campus oasis? That's what we, Anne Cetto and Austin Mills, are here to investigate.

We began our study, trowel in hand, under the Subway overhang among the Common Boxwood shrubs. After practicing the proper sterilization techniques and removing the light layer of pine-straw mulch, we dug approximately one inch into the top soil layer to collect our sample. The soil in this location was cool, moist, and slightly compacted. The sampling site is located on a slope and likely comes in contact with a high amount of water runoff and pedestrian traffic.

Sampling area in front of the BSC Subway and C-store

After returning to the lab, we plated a series of diluted samples on four different laboratory bacterial growth plates. An additional plate contained a medium that was designed to grow only fungus so that we would be able to create a ratio of bacteria to fungus contained within the soil sample. These plates can be seen in the photos below.

Growth plates are pictured with the far left plate being the most concentrated sample.  The fluorescent pink plate selects for fungus as opposed to bacteria.

Growth after five days.

Growth after five days.

As seen in the above photos, the most growth occurred on the plate with the highest sample concentration. Amount of growth decreased as the sample concentration decreased, with no growth on the plate containing the least concentrated sample. As our investigation continues, we will keep you posted with the most recent information - don't forget to check back with us next week!

- Austin and Anne