When you think of sloths, what comes to mind? Slow, furry animals with faces emitting sleepiness? Poor creatures who may wish to move a little more efficiently, but whose snail-speed bodily reactions give them no other choice than to be slow? A certain three-toed, Zootopian sloth whose laugh became a feeding ground for 2017 memes? These multi-talented mammals have much more to give: in recent days, a group of scientists working in Costa Rica found that sloths may lead us to the discovery of antibiotics that can kill superbugs.
What Are Superbugs?
Superbugs, in other words, are “antibiotic-resistant bacteria,” which are microorganisms that have evolved entirely from human actions. When penicillin, an antibacterial compound, was discovered in 1945, an antibiotics craze drove humans to quickly adapt to the everyday use of antibiotics. With great antibacterial power, however, comes great responsibility that those who came before us did not assume. Due to the rise in antibiotic usage, bacteria without antibacterial resistance were repeatedly eliminated, while the ones with rare genetic mutations that granted resistance to antibiotics survived, reproduced, and ballooned in number. As a result, the first superbugs were born, paving the way for many more to come.
As antibiotics were introduced into our daily routines, a growing number of superbugs with a wider range of antibiotic resistance were produced through the process of natural selection. So much so, that the World Health Organization estimates that resistance to antibiotics could lead to ten million deaths a year in 2050. Since these superbugs are still infectious and often fatal, the search for scientists is anti-superbug molecules to introduce to pharmaceuticals is neverending.
Why Are Antibiotics on Sloths, of All Animals?
Sloths can be thought of as a slower and furrier version of Atlas from Greek mythology. Like the esteemed Greek titan, who is said to be able to carry the weight of the Earth on his shoulders, the regular sloth can comparably support entire robust ecosystems.
Trichophilus, a species of green algae, can be found in a dense coat covering the fur of many sloths. The algae provide sloths with camouflage, and it grows with the help of sloth moths, small, brown insects that feed from the algae, and some of what is given off by sloth fur. Around 120 Sloth moths, which exclusively inhabit the fur of sloths, can be found on one sloth!
To fully grasp the enormity of the microbiome inside sloth fur, electron microscopes must be used. Only microscopes as powerful as these can create the high-resolution images needed to view these microorganisms. Scientists found “caves” in each strand of two-toed sloth fur, all filled with numerous bacteria and fungi. The small cracks found on the surface of the smoother three-toed sloth hair house fewer microorganisms.
A previous study revealed that the culturable fungi on two-toed sloth hair produce antibacterial and antiparasitic substances and can kill parasites such as Trypanosoma cruzi, which can lead to serious heart and digestive problems. The discovery catalyzed a new inquiry into the total number of antibiotics living in sloth fur and spoke of further discoveries merely waiting to be made, but no noteworthy research was devoted to the topic until a caretaker of sloths in Costa Rica noticed a particular pattern in the health of sloths in her sloth sanctuary received.
What Drew Scientists’ Attention to Sloths?
American Judy Avey, who has been directing the Costa Rican Sloth Sanctuary with her late husband, Luis Arroyo, for thirty years, noticed that the sloths the establishment has nurtured have never been ill or infected.
“We’ve received sloths that had been burned by power lines and their entire arm is just destroyed,” she said, “and there’s no infection.”
Samples from the fur of two-toed and three-toed sloths were taken to study to explore this anomaly.
As a result, a team of scientists led by researcher Max Chavarria investigated the two species of sloths native to Costa Rica: Bradypus variegatus, a species of three-toed sloths, and Choloepus hoffmanni, a species of two-toed sloths. Fur samples were taken from thirteen three-toed sloths and fifteen two-toed sloths, all of which resided at the sanctuary. The hairs were scrutinized under an electron microscope. In short, scientists found that Actinobacteria, a phylum of bacteria that houses antibiotic, antifungal, and anticancer microorganisms, and Firmicutes, a phylum that includes bacteria that improve metabolic and immune health, are commonly found in the fur of both species. Furthermore, nine species from the Brevibacterium and Rothia genera, which house both pathogenic and beneficial organisms, produced substances that prevented common mammalian pathogens, and disease-causing microorganisms, from growing by competing with the pathogens for nutrients and other resources. All the antibiotic organisms were actively engaging in a mutually-benefiting relationship with the sloths themselves: sloth fur provided the bacteria with nutrients and, in return, the bacteria rid sloths of many antibiotic-resistant superbugs.
What was the Procedure?
First, the team used DNA-identifying processes to isolate and identify the bacteria that produced possibly-antibiotic compounds in each sample of sloth fur. They found three notable species of bacteria, all of which belonged to Micrococcus, an order of bacteria in the phylum Actinobacteria. Then, they began testing the compounds’ effectiveness against superbugs.
Prior to the experiment, no pathogens had been discovered in sloth fur. So, the scientists introduced pathogens and tested each of them on the three species of bacteria. The pathogens included Escherichia coli, which can cause nausea, diarrhea, stomach cramps, and vomiting, Pseudomonas aeruginosa, which leads to blood, lung, and other infections, and Bacillus spizizenii, which causes food poisoning. All were obtained from the American Type Culture Collection, which sells samples of microorganisms for research. The scientists also tested fungi, including Fusarium sp., the source of skin infections, Cytospora sp., a skin-infecting fungus that has not been officially declared a mammal pathogen, and Trichoderma sp., which can lead to plant diseases, such as root rot, fruit rot, and wilting.
First, scientists placed each superbug in separate petri dishes to be able to identify any pathogens that the antibiotics were effective against after the experiment. They then grew each superbug in separate Petri dishes by feeding them with agar, a jelly-like substance used in cell culturing. Next, pieces of agar containing each of the potentially-antibiotic molecules were placed on the surface of each petri dish. Filter paper promoting bacterial growth was placed on each of the Petri dishes, which were later incubated.
Five strains, or species with similar characteristics, of antibiotics-producing bacteria were found on two-toed sloth fur, and four strains of different antibiotic-producing bacteria were found on three-toed sloth fur. All nine species of bacteria can be grouped into one of three main categories: Brevibacterium sediminis, Rothia koreensis, and Rothia kristinae. Although the study did not specify which microorganisms B. sediminis could fight off, it did find that R. koreensis and R. kristinae were both effective against bacteria such as S. aureus, which causes skin and soft tissue infections. R. kristinae was also found to be effective against E. coli and Pseudomonas aeruginosa, which are naturally resistant to almost all antibiotics, making it a significant health problem. All three Microccocineae secreted substances that fended off Cytospora sp., which suggests that Micrococcineae can evolve the ability to ward off harmful, non-bacterial microorganisms. Therefore, over time, Micrococcineae in sloths could expand the range of pathogens that their secreted substances kill and prove even more valuable to humans.
So What?
The misuse of antibiotics over the last few decades has become a major worldwide health issue. Novel antibiotic-resistant, infectious organisms have evolved as a direct result of our actions. Hopefully, the discovery of antibiotics living on sloth fur will guide humans toward the development of effective compounds against superbugs. When golden opportunities for improving our immunity to infectious diseases confront us, no time should be wasted in seizing them.
Future research revealing the exact pathogen-removing compounds produced by the bacteria would lead to the production of medications that effectively defeat four of the eighteen superbugs known to us. Of course, four is considerably less than eighteen, the total number of superbugs in existence, but progress rarely comes in great leaps; instead, it creeps forward, inching its way to a milestone.
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