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Hidden Life Beneath Our Feet: How Pesticides Shape Soil Microbial Diversity and Immune-Relevant Microbes

CSEF · 2026 Microbiology (Junior Division)

Rojan Sanati

Overview

Have you ever wondered how the chemicals used in your garden or backyard might impact not just plants, but also the invisible world beneath your feet and even your own immunity? According to the hygiene hypothesis, exposure to pesticides can deter immune alertness, causing immune dysfunction. However, higher exposure to diverse environmental microbes has been correlated with improved immune tolerance and reduced risk of allergies and autoimmune disorders. The purpose of this project is to determine whether pesticide use in local gardens reduces soil microbial diversity, and why these findings may matter for your health and our environment. Grasping this impact can inform safer gardening. Soil samples were collected from various locations, including heavily pesticide-treated soil (White Rose Soil), non-treated soil (Clovis Botanical Garden), and nutrient-rich soil with targeted pesticide application (Shinzen Garden), to show how different levels of pesticides affect microbes. The samples were cultured on sterile nutrient agar plates and were left to incubate for about 96 hours. Colonies were organized by their composition, such as color and texture. Microbial diversity was assessed using total colony counts and the Shannon Diversity Index. I hypothesized that Clovis Botanical Garden would represent the most microbial diversity, harboring the highest SDI. However, results showed that although there were differences in colony counts, the t-Test and Shannon Diversity Index confirmed the rejection of the null hypothesis, indicating no statistically significant difference was found. This shows that if pesticides are used sparingly, then it has little to no difference on soil microbial diversity. These findings shine a light on the crucial role of considerate gardening practices for all public health.

Competition history

  • CSEF 2026 Microbiology (Junior Division) · Entry J-16-06

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