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Figure 3.1. Functional Biodiversity Straw vs. No Straw
Note: The graph shows the utilization efficiency of different carbon sources (carboxylic acids, amino acids, carbohydrates, polymers, & amines) from the microbial communities between our C1 & C2.
NOTE: During the placement of the conditions into the EcoPlate, we mistakenly used the wrong dilution of C1 (straw) soil solution for well placement . However, upon comparing data with peers who conducted the same experiment, we found no great deviation from the standard and proceeded to treat the data as normal.
Figure 3.2. Shannon Biodiversity Index (H)
Note: Box and whisker plot showing the range of Shannon Diversity Index values calculated by the formula indicated in the Method section for C1 (Straw) and C2 (No Straw) from a sample size of 7. The mean H value from each condition is indicated by the "X". The p-value was calculated through an unpaired t-test with unequal variance to receive 0.083. As it was larger than the significance value of 0.05, we do not have enough evidence to support the hypothesis that there is a difference between the biodiversity of Condition 1 and Condition 2.
Figure 3.3. Richness Values (S)
Note: Box and whisker plot showing the Richness values calculated using the formula indicated in the Method section for C1 (Straw) and C2 (No Straw) from n = 7. "X" marks the mean from each condition. The p-value was calculated through an unpaired t-test with unequal variance to receive 0.084. As it was larger than our significance value of 0.05, we do not have enough evidence to show a significant difference between the utilization of carbon sources between the two conditions.
Figure 3.4. Evenness Value (E)
Note: Box and whisker plot showing the Evenness values calculated using the formula indicated in the Method section for C1 (Straw) and C2 (No Straw). X marks the mean from each condition. The p-value was calculated through an unpaired t-test with unequal variance to receive 0.223. As it was larger than our significance value of 0.05, we do not have enough evidence to support a hypothesis that there was a significant difference between the utilization of different carbon sources by our two conditions.
Method
Results were compiled from a series of analyses based on data collected from the EcoPlate, which is a multi-well plate that contains 31 different carbons sources in three groups. Microbes interact with those carbon sources and turn varying levels of purple depending on the severity of utilization. Three groups were tested (control, C1 (straw), & C2 (no straw)).
First, soil samples were vortexed and diluted twice to extract the isolated microbial community by pipette before being placed into their assigned group wells. After the absorbance of the wells at 595 nm was read by spectrophotometer, the initial A595 were recorded, and the plate was incubated for a week.
The A595 were recorded again and both initial and later data were inputted to an Excel worksheet. From there, we calculated the change in A595 across all three groups and adjusted delta absorbance along with any negative change. Values above 0.25 were considered substantial change and were counted as proper utilization of the carbon source.
Richness (S) values for the two conditions were calculated by summing positive wells (wells with values above 0.25) to compare the number of different carbons sources utilized by the microbial community in C1 and C2.
Shannon Diversity Index (H) values were calculated for each condition with the formula -1 × Σ(Pᵢ × ln(Pᵢ )), where Pᵢ is the delta absorbance divided by the sum of all delta absorbance for that condition. The H values of both conditions would be compared later.
Evenness (E) values were calculated by the formula H / ln(S) to compare how evenly the microbial community in each condition would utilize different carbon sources.
Evidence
Visually, there was no difference in relative carbon utilization efficiencies of the microbial communities depending on presence of straw. This means that the bacterial community between the two conditions were more similar than not. The greatest difference in carbon source utilization efficiency was the amino acid group with a difference of 2%. However, the average percent difference between the two conditions was 1.2%.
From Figures 3.2 - 3.4, one could assume that the values received for condition 1 and condition 2 were different from each other. However, upon taking the t-test of H, S, and E, one can see that the differences between the values calculated was likely due to chance and not because of a certain reason due to all the values being higher than 0.05 (0.083, 0.084, and 0.223).
We can confidently conclude that the soil in Condition 1 and Condition 2 are similar enough that there is no significant difference between the microbial make up of both locations. Our calculated p-value is not small enough to support the alternative hypothesis. The most obvious reason for the H, S, and E values being similar between the two conditions is that the microbial make-up of the two conditions are the same, if not very similar.
Conclusion
Even taking into account how the first two rows of the EcoPlate under our condition 1 had an erroneous different process, our data for the carbon source utilization efficiency seemed to be fine. Thus, the likelihood that the similarity of the two conditions is due to chance is low but not zero.
Explanation
We are confident that it is likely that even though the two conditions were taken from a different location, that their biodiversity is still the same or similar enough. Based on how none of our significance values for the Shannon Diversity Index (H), Evenness (E), and Richness (S) were significant, which signifies that the differences between H, E, & S were due to chance. The most likely leading hypothesis at this point would be that the biodiversity in the soil of the garden is of the same make up.
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