The Effect Of CarbonDioxide Availability On Bacterial Growth And Antibiotic Sensitivity

Grade:

9

Teacher:

Alfred Santos

This study investigated the effect of carbon dioxide (CO₂) exposure on bacterial growth and antibiotic sensitivity in Escherichia coli. The objective was to determine whether elevated CO₂ levels alter bacterial susceptibility to antibiotics, which may have implications for environmental and medical microbiology. A Kirby-Bauer sensitivity assay was performed using penicillin and streptomycin antibiotic discs. Bacterial cultures were prepared using a 0.5 McFarland standard and evenly spread on TSA agar plates. CO₂ was generated through a chemical reaction between citric acid and baking soda and used to expose experimental bacterial samples for 30 minutes before incubation at 35 °C for 24 hours. Zones of inhibition were measured and compared between CO₂-exposed and unexposed bacterial samples. Statistical analysis was conducted using a two-sample t-test. Results showed that CO₂-exposed E. coli had smaller zones of inhibition for both antibiotics, indicating reduced antibiotic sensitivity. Penicillin showed a large decrease in inhibition, with the mean zone decreasing from 28.67 mm in unexposed samples to 8.67 mm in CO₂-exposed samples (p = 0.05), demonstrating borderline statistical significance. Streptomycin also showed a reduction from 27.33 mm to 21.00 mm, although this change was not statistically significant (p = 0.067). These findings suggest that elevated CO₂ conditions may alter bacterial physiology and reduce antibiotic effectiveness, possibly due to changes in pH, metabolism, or stress responses. This study demonstrates that environmental CO₂ levels may influence antibiotic sensitivity in bacteria. Understanding these effects is important for predicting how environmental changes could impact antibiotic resistance and public health outcomes.

Project presentation

Research paper