Antibiotics in Your Backyard: Locating Antimicrobial Plants in Our Environment

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Antibiotics in Your BackyardLocating
Antimicrobial Plants in Our Environment
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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.

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Gram Positive Bacteria
Bacteria are classified as either Gram positive
or Gram negative based on different structural
characteristics

• Gram positive bacteria have cell walls made
  mostly of peptidoglycan

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Gram Negative Bacteria

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

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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
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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.
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A Bioassay Plate
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Extractions

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

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Brine Shrimp Bioassay

• If a compound kills brine shrimp, it is likely to
  act as a pesticide and kill insects, and other
  pests

• Detects naturally occurring pesticides in plants

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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

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Results

• What We Found

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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.
Johns 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.
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Whats Next?

• New antibiotics
• Various pharmaceuticals
• Food preservation
• Industrial applications
• Safe and natural pesticides

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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.
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Acknowledgements

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