The platypus has long fascinated scientists, with its weirdly unique assortment of features making it one of the most unusual animals on the planet. Now a team of Australian researchers has found that platypus milk contains novel antimicrobial properties that could help scientists battle the global superbug threat.

The platypus, along with four species of echidna, are the only surviving examples of monotremes in the world today. Hypothesized as splitting off from other mammal lines around 200 million years ago, monotremes are defiantly odd animals – and platypuses even more so. They lay eggs like reptiles but produce milk to feed offspring like mammals.

Several years ago it was discovered that platypus milk contained unique antimicrobial properties. This discovery made complete sense, as platypuses have no teats, so milk is expressed through pores on a mother's abdomen. The milk pools in grooves from which her offspring lap it up, but this process significantly exposes the milk to bacteria in the environment.

Researchers at CSIRO and Deakin University have uncovered a unique protein in the milk that is likely to be responsible for its amazing antimicrobial properties.

"We were interested to examine the protein's structure and characteristics to find out exactly what part of the protein was doing what," explains Julie Sharp from Deakin University.

The team managed to successfully replicate the unusual protein in a laboratory setting and found a type of folding structure that has never been seen before. The protein was found to have a novel ringlet-like formation and has since been called the "Shirley Temple" protein in reference to the famous child-actor's curly hair.

This unique protein is only present in the milk of monotremes and is found in high concentrations. While it may have other roles to play in the development of the young animals, the researchers hypothesize that this novel protein may have evolved to support the unusual lactation strategy of monotremes, protecting the young from bacterial contamination in ways that are simply not an issue for mammals that suckle directly from a mammary gland.

"Although we've identified this highly unusual protein as only existing in monotremes, this discovery increases our knowledge of protein structures in general, and will go on to inform other drug discovery work done at the Centre," says Janet Newman from CSIRO.

This isn't the first time our weird platypus friends have suggested novel new medical pathways that could help humans. In 2016 a group of South Australian researchers discovered monotremes hold a novel form of a hormone that could assist scientists in developing new treatments for type 2 diabetes.

The research was published in the journal Structural Biology Communications.

Source: CSIRO

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