Antibiotics are one of humankind’s most amazing discoveries. Ever since that fateful day in 1928 when Scottish physician Alexander Fleming noticed a funny mold growing in one of his
petri dishes, antibiotics have been kicking bacterial butt.
That famous mold, of course, was producing penicillin, the founding antibiotic superstar,
which has since extended the average human life by at least a decade. It fundamentally
changed the face of medicine. Antibiotics, or antimicrobials, are basically selective
poisons designed to either kill or slow the growth of bacteria to the point where your
body’s own immune system can clean up. These drugs target a specific part of bacteria or
some important stage in their development without damaging the body’s host cells. And
they’re really great their job. Until they aren’t.
Lately, antibiotic technology has been having a hard time keeping pace with bacterial evolution.
We’ve talked here on SciShow about how lots of your die-hard, go-to favorite antibiotics
are starting to lose their mojo in the face of sneaky and rapidly evolving bacteria. The
US Centers for Disease Control and Prevention estimates that at least 2,000,000 Americans
became infected with drug-resistant bacteria in 2012, and 23,000 of them died as a result.
These superbugs are deadly serious and could quickly unleash a global health crisis if
we don’t find a way to keep them in check. The problem is we’ve already hit up many of
the most obvious sources of antibiotics, like fungi, which includes penicillin, and synthetic
molecules. Fortunately, we humans have big, delicious
brains, and some of the best of them are hard at work trying to invent all-new ways to kill
dangerous bacteria or find other organisms on the planet that are better at it than we
are so we can steal their secrets. And while they’re finding some promising leads, I gotta
say, they’re looking in some pretty weird places.
You know how everyone jokes that after some big global disaster, only cockroaches will
survive? Well, we recently found what may partially explain their famous, and infuriating,
tenacity. Research from the University of Nottingham suggests that certain insects,
like roaches and locusts, have brain tissues that are infused with super-powered antibiotic
juju. The researchers found nine different antibiotic molecules tucked into the roaches’
nervous systems that may be protecting them from otherwise lethal bacteria. They’re all
a type of molecule known as peptides, short chains of amino acids that make up proteins,
kinda like proto-proteins. And these peptides are specific to the bugs’ brains. They seem
to be chemicals that roaches” brain cells use to communicate with each other, y’know,
whenever a cockroach is sitting around thinking about stuff, which I guess can happen, and
although we’re not sure how these peptides actually work, laboratory tests have shown
that they’re incredibly effective at eliminating some of our least favorite bacteria, like
the most dangerous strains of e.coli, which cause gastrointestinal infections. And even
MRSA, a super-resistant type of staphylococcus bacterium that can cause unstoppable deadly
infections in humans, particularly in hospitals. In lab trials, these roach brain molecules
killed over 90% of MRSA bacteria, without harming any host cells.
So I can guess what you’re thinking: shut up and take my money! Well, hold on a sec,
because we’re a bit away from having cockroach brains on the pharmacy shelves. There’s still
loads of technical hurdles to overcome, tests to conduct, basic things we need to figure
out, like how exactly these molecules work. But roaches aren’t the only hardy animals
out there. Alligators are some of the Earth’s most rugged beasts. They essentially live
in cesspool swamps teeming with bacteria and fungus and other microbes, and more than that,
they’re known brawlers. Put just a few territorial 800 pound toothy reptiles together in a dirty
swamp, and you will no doubt come out with some serious bite marks and bloody wounds,
even missing limbs. But amazingly, what you probably won’t find are any infections. This
got some bayou scientists to thinkin’! Dr. Mark Merchant, a biochemist at McNeese
State University in Louisiana, helped conduct a decade long study that investigated what
makes alligators so unusually resistant to bacterial and fungal infection.
Turns out, it’s in their blood. An alligator’s immune system is largely innate, meaning it
can fight off harmful micro-organisms without having any prior exposure to them. They just
pop right out of their eggs ready to do battle. We humans also have some innate immunity,
provided by things like our skin and white blood cells, but a big part of our immunities
are adaptive, meaning we often develop a resistance to specific diseases only after being exposed
to them. Which of course is not ideal all the time, but alligators get to skip this
Researchers examining blood samples from American alligators isolated their infection fighting
white blood cells and then extracted the active proteins working in those cells. And these
two included a special class of peptides which seemed to have a knack for weakening the membranes
of bacteria, causing them to die. When pitted against a wide range of bacteria including
drug-resistant MRSA, these tough little peptides proved to be effective killers. They also
wiped out 6 of 8 strains of candida albicans, a type of yeast infection that’s particularly
troublesome for AIDS and transplant patients with weakened immune systems. Such compounds
may also be found in similar animals, like crocodiles, Komodo dragons, and the skins
of some frogs and toads. So far, lab trials have shown that gator blood can kill at least
23 different strains of bacteria including salmonella, e.coli, staph, and strep infections
AND even a strain of HIV. For now, scientists are working to find the exact chemical structures
at work in four of these promising chemicals and pinpoint which types are best at killing
which microbes. One problem so far: high concentrations of gator blood serum have already been found
to be so powerful that they are toxic to human cells. So other biologists are taking a different
approach in the search for the next generation of antibiotics.
Rather than looking at other animals, they’re exploring strange, new places, like cave soils
and deep-sea sediments. Researchers have recently discovered evidence of promising new fungi
strains living way down in hundred million year old nutrient-starved sediments in the
Pacific Ocean. Everyone thought this was a near-dead zone for life, too harsh and remote
an environment for something like fungi to survive in. Just a decade ago, the only living
things known to inhabit such deep sediment layers were single-celled bacteria and archaea,
organisms known to flourish in extreme environments. But while examining dredged up sediments from
as deep as 127 meters into the sea floor, scientists found fungi of at least eight different
types, four of which they successfully cultured in the lab. Some of the fungi even belonged
to the genus Penicillium, which we have to thank for the development of penicillin. Now,
we’re not exactly sure how old these fungi are, but they are definitely quite old and
maybe, more importantly, they appear to have been living in isolation for eons. If that’s
the case, they may have evolved specific and unusual defenses against bacteria, which,
just like their penicillin kin in that famous petri dish, could end up being a new and powerful
source of antibiotics. And there’s one more strategy that scientists
are using, one that works in espionage as well as in medicine. And that is seeing what
the enemy is up to. While exploring life in strange new places
around the world, some biologists are looking for bacteria that have never been exposed
to our drugs, but still appear to be naturally resistant to them.
Wherever we find the most naturally resistant bacteria, we might also find natural antibiotics
that we never knew about. And here, one of the most promising leads
is again in one of the hardest-to-reach places: New Mexico’s Lechuguilla cave, a place that
was isolated from all human contact until it was discovered in the 1980’s.
One of the many fascinating things that scientists have discovered here is that the cave bacteria
seem to be resistant to everything. Even though they’ve never been exposed to
us or our drugs, all of the bacteria have proven to be resistant to at least one major
antibiotic, and many tend to fend off more than a dozen of the most powerful antimicrobials
we have. This suggests to scientists that the bacteria have evolved to be this way because
they live in an environment that’s rich in naturally occurring antibiotics, ones that
the germs we live with up here on the surface have never encountered.
Now we just have to find out what exactly those compounds are.
So look, I’m not going to lie to you: we have a lot of work to do.
While we might discover a new super-drug lurking in a cave or under the sea or in a cockroach’s
head, there’s a big difference between finding a substance that cleans house in a petri dish
and actually putting a new antibiotic in the vein of a human patient.
So the bummer is, as promising as some of these bold new discoveries may be, none of
them has yet yielded an actual marketable drug.
Still, there’s a long list of successful antibiotics that we’ve managed to derive from strange
sources, starting with Dr. Fleming’s rogue fungus.
So if we keep exploring strange new places and studying how other animals deal with the
problems we’re facing, we just might find the next penicillin before the superbugs get
the best of us.
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