Antibiotics in Your Backyard : Locating Antimicrobial Plants in Our Environment

Our Project We tested many plants in our environment in order to locate these important antimicrobial compounds. What We Were Looking For  Antibacterial compounds that kill or inhibit the growth of prokaryotic cells.  Pesticidal compounds that kill organisms in the phylum annelidia, such as worms, and arthropodia, such as insects.

Gram Positive Bacteria Gram positive bacteria have cell walls made mostly of peptidoglycan Bacteria are classified as either Gram positive or Gram negative based on different structural characteristics

Gram Negative Bacteria Gram negative bacteria have lipopolysaccharides, lipoprotiens and other macromolecules surrounding their peptidoglycan cell walls.

Pediococcus and E.coli Bacteria Bioassay Detects antibacterial compounds that kill or inhibit the growth of Gram positive bacteria and Gram negative bacteria Pediococcus is gram positive E.coli is gram negative

Yeast Bioassay Detects antifungal compounds that kill or inhibit the growth of fungi. Bioassay Plates Used to locate antibacterial and antifungal compounds Contain media (food) for a certain bacteria or fungus to grow Samples of plants we hope will inhibit the growth of the microorganism are placed on hole punched filter paper.

A Bioassay Plate

Extractions Hexane and ethanol extractions Oils partition into non polar hexane Proteins and sugars partition into polar ethanol

Brine Shrimp Bioassay Detects naturally occurring pesticides in plants If a compound kills brine shrimp, it is likely to act as a pesticide and kill insects, and other pests

Brine Shrimp Bioassay We would have added plant extracts into petri dishes containing live brine shrimp. If the brine shrimp were dead the next day, we would have concluded that the plant contained pesticidal compounds

Results What We Found

Bioassay Results We tested for antimicrobial compounds in plants in the environment. The ethanol extraction of garlic killed yeast. Therefore, its proteins and sugars are antifungal. Due to massive mentor error, we were unable to test St. John’s Wort flower successfully. If the experiment had gone as planned, its proteins and sugars would have show antibacterial properties. One of our plants provided an odd substance that grew in media without bacteria. We tested it again and found that it killed Pediococcus bacteria, suggesting it is antibacterial. This substance was found in the ethanol layer extraction, meaning it is in the proteins and sugars of the plant.

What’s Next? New antibiotics Various pharmaceuticals Food preservation Industrial applications Safe and natural pesticides

Conclusion This week, we randomly tested numerous plants located around the OSU campus. We found that the garlic killed the fungi and that the mysterious leaf (substance) killed Pediococcus. There really are antibiotics in your own backyard. So save the environment.

Acknowledgements Rachel McKenna, Mentor, Bioengineering, high school Lili Chu, Mentor, Bioengineering, Oregon State University Dr. Michelle Bothwell, Bioengineering, Oregon State University