Mold is for Wimps: Antibiotics from Big Scary Reptiles

Mold is for Wimps
Antibiotics from Big Scary Reptiles

They're not after a nice pair of crocodile skin boots. They're not after a big trophy head to hang on the wall. They're tromping around the billabong for something much more important than that. What they want is a sample of crocodile blood. Don't worry, crocs, these hunters aren't going to kill you, they just want to stick you with a needle and then let you go.

Gill Diamond

Gill Diamond is a scientist at University of Medicine and Dentistry of New Jersey. He is fascinated by the giant salt water crocodiles that swim in the swampy rivers and billabongs of northern Australia. These are the largest reptiles on earth, growing up to 30 feet in length. It's not smart for a human to get near the jaws of one of these hungry beasts. It's not terribly safe for another crocodile to get near those jaws, either, and that is what caught Diamond's interest.

Scientists who study crocodiles in the wild noticed something peculiar. There are a lot of three-legged crocodiles swimming around. This is because crocodiles fight a lot, and often bite off each other's limbs in the process. This brought up a question: How can these crocodiles swim around in tropical swamps with giant bleeding wounds and not get infected? The waters of tropical swamps are teeming with microbes that cause all kinds of diseases. Many people in poor developing nations have to drink from such water sources, and that leads to high rates of infectious diseases in such places. But the crocs survive. Why?

The New Guinea crocodile

One person fascinated by this question was documentary film maker Jill Fullerton-Smith, who learned of this phenomenon when filming a television show about crocodiles. Fullerton-Smith then brought this puzzle to the attention of scientists like Gill Diamond.

Scientists suspected that the crocodiles might have some compound or compounds in their blood that helps fight the microbes that live in the swamp waters. So Diamond began to investigate crocodile blood. Isolating antibiotic proteins from crocodile blood isn't easy to do. Someone has to carry out the not-so-easy task of catching wild crocodiles, taking blood samples, and then releasing the not-so-happy crocodile back into the water. But Diamond was able to isolate a peptide that might function as an antibiotic. Peptides are short chains of amino acids, shorter than proteins. The peptide has been named crocodillin, and as Diamond puts it, crocodillin “blows away” bacteria. Crocodillin can even kill resistant bacteria, and it seems bacteria have a hard time developing resistance against it. More research needs to be done on the protein before it can be used as a drug, but it could turn out to be the next big wonder drug.

(Even though you can't get a prescription for crocodillin yet, it turned out to make good television. Fullerton-Smith chronicled Diamond's search from crocodillin in her BBC documentary The Secret Life of Crocodiles.)

But crocodiles aren't the only large carnivorous reptile that Diamond is looking to for tomorrow's miracle cures. The Komodo dragon, the world's largest lizard, lives on the island of Komodo and nearby isles in Indonesia. This monster can grow to be 10 feet long has been known to eat people and anything else that gets in its way, including other Komodo dragons. We aren't painting a pretty picture of this animal, and it only gets worse. The Komodo dragon is a scavenger as well as a hunter, and the dead animals it finds and eats are often rotten and crawling with disease-causing microbes...mmm! Our pal Komodo turns this to its advantage when hunting. Often, it doesn't attack and kill its prey, but just gives it a good bite on the leg, for example, then lets the prey run away. Since Komodo has been feeding on infected carrion, its saliva is filled with deadly microbes. When Komodo bites its prey, the prey gets infected, and soon dies. When this happens, Komodo returns to chow down on the dead animal.

Komodo's use of biological warfare to kill its prey made Diamond wonder about something. Why don't the deadly microbes kill the Komodo dragon? So he began to study the bodily fluids of Komodo dragons, again looking for compounds with antibiotic substances. Who knows? A drug found in the Komodo dragon may save your life someday.

The natural world is a place of fierce competition. Penicillium mold produces penicillin to protect itself from the onslaught of bacteria. Since bacteria can infect any organism, it's only logical that other organisms, including big scary reptiles, might produce antibiotics to protect themselves as well. Whether or not killers like the salt water crocodile and the Komodo dragon will become life-saving sources of antibiotics remains to be seen. But one thing is for certain. Alexander Fleming, Howard Florey, or Ernest Chain never had to worry about getting an arm bitten off by a penicillium mold!
Video clips

Clip 1 — Gil Diamond explains his interest in komodo dragons, 6.83 MB (audio only, 279 KB).

For more information, at other Web sites...

Croc Blood Battles Superbugs — news article about crocodillin from BBC News, featuring an audio interview with Jill Fullerton-Smith.
Crocodile Cure — the story of how documentary filmaker Jill Fullerton-Smith helped bring crocodile immunity to the attention of pharmaceutical science, from The Open University.

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Image Credit

The New Guinea Crocodile: Photo by Philip M. Hall, copyright © 1996 Crocodile Specialist Group, University of Florida.

Copyright ©2002 The Chemical Heritage Foundation