The Microbes Within

The soil beneath the boxwood revealed a host of microbes within the soil. The 10-3 diluted solution contained the most colonies and was the plate used to calculate the average number of microbes per gram of soil. Counting 72 individual colonies then multiplying by 10-3, we determined that within our soil sample there are 72,000 microbes per gram of soil. Incredible! Within one gram of soil there exist thousands of microbes. Imagine what you could find within a square foot underneath the boxwood! But this begs the question: are all of the microbes in the one gram of soil from the same species or is a wide array represented?

Simply observing the plates allows the deduction that more than one microbe species are present. As the solutions increased in dilution, the amount of microbes decreased which allowed for specimen isolation. There were various bacteria colonies ranging from yellow to creamy white, from lumpy to smooth. Furry fungi could be found on the 10-3, 10-4, and 10-5 diluted solution plates. Interestingly, the fungi on the 10-5 plate had a bright red hue. The 10-4 diluted solution on the Rose-Bengal agar plate only had one large specimen. Being convex, smooth, and creamy white, it's appearance was more similar to a striped boil than a microbial colony.

So why do these observations of various microbes matter? Though the soil underfoot does not always appear to be more than solid ground, the biodiversity within plays a vital environmental role. Think of soil as the support system for all living things existing above. Not only physical support, but also nutritional. Microbes within soil are the key recycler of organic material produced from organism living above the dirt and supply nutrients back to environment for consumption. They affect the acidity and sodicity of soil, which must be maintained for proper plant growth. These tiny organisms act as a filtration system, purifying water and other solutions that pass through soil. What is important to remember is that though microbes are small, they powerful environmental allies.

-Palmer Miller

Beneath the Boxwood Bush

In the early afternoon of February 10, we began the process of searching for microbes hidden in the ground, found in soil around the campus of Birmingham-Southern College. During the next several weeks, we will be performing experiments and recording observations on our soil sample to determine the microbes found in the soil. We collected our soil directly beneath a boxwood bush and nearby several holly bushes. The temperature on 02/10/15 had a low of 30° F and a high of 48° F, while the temperature was 46° F when our sample was collected. The ground was cold, in comparison to an average day of warmer temperatures and found in a shaded area under the boxwood bush. The soil was rocky and abnormally dry, with rainfall accumulating only 0.06 inches over the past nine days. Air humidity was also low in comparison to humidity levels during warmer days. Below are photographs of the geographical nature and habitat of the location where soil was collected. 15 mL of soil was removed from the ground, but the habitat was left unharmed. 0.5 g of soil was mixed into 50 mL of sterile water, and then diluted to form solutions 10^-3, 10^-4, 10^-5, 10^-6, 10^-7. These solutions were transferred to appropriately labeled Petri dishes containing tryptic soy agar, with an additional plate of Rose-Bengal agar with the 10^-4 dilution. The Petri dishes were left to incubate at room temperature for seven days. We will be updating this post about the progress of microbial growth on the Petri dishes on day 7.

On day 7, our preliminary results showed various growth patterns on each of the six Petri dishes, shown below. The diluted solution 10-3 had the largest microbial growth showing multiple circular, large colonies that were milky white. The 10-4 solution had less colonies but had an abnormally large colony with few smaller colonies surrounding it. Diluted solutions for 10-5 and 10-7 showed less and less microbial growth, with only one or two colonies present. However, the diluted solution at 10-6 had a larger, red colony on the edge of the plate and was the only solution that had microbial growth of a different color than milky white. The solution on the Rose- Bengal agar with 10-4 dilution had one large, circular, milky white colony present.

- Heather Daniel