SCIENCE

A new class of microorganisms kills drug-resistant “superbugs”—and lives in dirt. (Washington Post)

Learn more about antibiotics and the biotics they target with our Q&A here.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

Discussion Ideas

• New research outlines the discovery of a new strain of antibiotics found in dirt. What are antibiotics? Use our resource here for some help.
  • Antibiotics are substances that can stop or slow the growth of certain living (biotic) microbes, such as bacteria. Penicillins are probably the most famous strain of antibiotic.

• How did antibiotics end up in dirt?
  • They live there! Researchers think the new microbes used as antibiotics are part of soil’s microbiome. Billions of identified and unidentified bacteria, fungi, and even microscopic animals make up the living (or once-living) parts of a thriving ecosystem … of dirt.

• What are malacidins? Read through the Washington Post article for some help.
  • Malacidins (metagenomic acidic lipopeptide antibiotic-cidins) are the newly discovered class of natural antibiotics (cidins) described in the research. Researchers say malacidins are commonly encoded in soil microbiomes.
    • Malacidins are toxic to drug-resistant “superbugs” such as methicillin-resistant Staphylococcus aureus (MRSA). Malacidins “work by interfering with the process that bacteria use to build their cell walls. Human cells rely on a different process, so the antibiotic isn’t toxic to people.”
      • Learn more about MRSA and antibiotic resistance with our resource here.
    • Scientists aren’t sure what microscopic species malacidins belong to. They have identified molecules—the “genetic blueprint”—but not the bacteria itself.

• Malacidins may be as old as dirt. Why are they just being discovered now?
  • There’s a lot of dirt in the world, and not a lot of people are analyzing it. According to researchers, most bacterial cultures used to create antibiotics “remain hidden in the global microbiome.”
  • New tools and methodologies are allowing scientists to identify and discover elements in the soil, seafloor, ocean water, freshwater, and even insect guts.

• The new research is a study in metagenomics. What is metagenomics?
  • Metagenomics describes the study of genetic material taken directly from environmental samples.
    • Most genetic studies are conducted from microbial cultures, in which microbes are allowed to reproduce in a medium (such as agar) under controlled conditions.
      • Although malacidins were identified in a metagenomic study, they were injected into a traditionally cultured microbe. “Soon enough, those microbes were making malacidins. When applied to cuts in the skin of MRSA-infected rats, the previously unknown molecule successfully sterilized the wounds. The bacterium didn’t show signs of resistance, even after three weeks of exposure.”
    • Metagenomics also includes study of ancient human genomes—not a part of soil’s natural biome—in cave dirt. Learn more about this “dirty DNA” with our resource here.

• How did citizen scientists contribute to the new research?
  • Citizen scientists did the data collection. Researchers “cloned vast quantities of DNA from hundreds of soil samples contributed by citizen scientists across the country.”

• So, when can we expect to see malacidin-derived antibiotics at the drugstore?
  • Possibly never. “It takes years for a novel molecule to be developed, tested and approved for distribution. But its discovery is proof of a powerful principle, he said: A world of potentially useful untapped biodiversity is still waiting to be discovered.”

TEACHERS TOOLKIT

Washington Post: A potentially powerful new antibiotic is discovered in dirt

Nat Geo: Antibiotic Resistance Q&A

(extra credit!) Nature Microbiology: Culture-independent discovery of the malacidins as calcium-dependent antibiotics with activity against multidrug-resistant Gram-positive pathogens