The tiny proteins can kill Gram-positive bacteria, opening doors for developing new antibiotics.
Newly discovered antimicrobial peptides could lead to treatments against dangerous infections from bacteria like methicillin-resistant Staphylococcus aureus (MRSA) shown above.
Image Credit: National Institutes of Health
Researchers from the University of Maryland, in collaboration with the National Institutes of Health have discovered a whole new class of antimicrobial peptides that could point the way to developing antibiotic alternatives for treating dangerous infectious diseases. The research was published in the journal Nature Communications.
Antimicrobial peptides, or AMPs, are small proteins formed by nearly all living things that help them fight off infections from microbes like bacteria and fungi. The mechanisms AMPs use to kill an attacking microbe have long interested scientists, who hope to adapt the same strategies for use in medications. Finding a completely new type of peptide that works in previously unexpected ways opens up an unexplored direction for anti-microbial research.
“These new AMPs are very small, and don’t look like what we would expect, so we’ve missed this entire category of natural antibiotics for years,” said Seth Dickey, assistant professor of Veterinary Medicine at UMD and lead author of the study. “But it turns out they are very powerful against Gram-positive bacteria, including drug-resistant strains like MRSA and vancomycin-resistant Enterococcus.”
Gram-positive bacteria are a class of bacteria that, although they typically respond well to antibiotics, are responsible for a large fraction of deaths due to bacterial infections. And overuse of antibiotics has meant many strains are developing resistance. “These new AMPs, which we named TMcins, kill bacteria in a new way, so they provide new and exciting ideas to treat bacterial infections,” Dickey said.
Dickey and his colleagues discovered the new AMPs while studying bacteria samples from a skin wound known as a Buruli ulcer. The team found strains of Staphylococcus aureus bacteria that were very good at killing other bacteria. Genetic analysis revealed a small piece of DNA that coded for an unrecognized antimicrobial peptide. The researchers then removed that DNA from the S. aureus bacteria and it lost its killing power. When they restored the DNA, its killing powers returned.
Additional research showed that the small peptides worked by creating large, stable pores in the membranes of other bacteria that allow interior contents to drain out. Surprisingly, TMcins did this by adopting a structure that was thought to be restricted to larger proteins. The researchers hope that this new peptide architecture can lead to new avenues of engineering antimicrobials.
In addition to showing that TMcins could kill several dangerous Gram-positive pathogens, the researchers found that the bacteria that produces them also produces companion molecules that help “chaperone” the TMcins as they move through their environment.
