Koala pouch may have its own bug buster
Marsupials such as koalas and wallabies may produce a unique antimicrobial substance to clean their pouches in preparation for their young, new research suggests.
Professor Elizabeth Deane of Macquarie University in Sydney has made the findings as part of research into how marsupials protect their young from microbial diseases.
Deane, who heads the university's environmental and life sciences division, said marsupial pouches are normally a breeding ground for potentially harmful microbes.
"[Pouches] are very dry; they have lots of brown material in them," Deane told ABC Science Online. "It looks like crud. It's crusty with what looks like dried secretions all over the place.
"In koalas in non-breeding season, you can lift wads of this brown stuff out."
But when the breeding season starts, the pouch becomes a completely different place, said Deane.
"It becomes glistening, pristine and almost translucent. You can go in and the back of it is almost see-through and you can see droplets of clear material on the pouch."
It's these clear droplets that Deane and a new PhD student are studying. They hope they will find clues as to how it's possible that tiny baby marsupials can fend off disease when they have no immune system of their own, and must crawl from the external birth canal, up through the mother's fur into the pouch.
"They are born very, very small after very short gestation periods of less than a month; they're about the size of a small baked bean or your fingernail and they have no nothing that provides them with an active immunological response," said Deane. "So their capacity to combat disease, as far as we can tell, is pretty low."
What protects the young?
Deane and team have been testing a number of theories about what protects the young marsupials, including one idea that the mother secretes antimicrobial compounds in her pouch at the time of birth. This is supported by the fact that other mammals produce antimicrobial proteins in part of their skin and gut.
While Deane is working with koalas and tammar wallabies, she has done most work in koalas.
She find koalas particularly interesting because they challenge one theory, that has been around for decades, that the mother licks the pouch clean before the young arrive.
While wallabies certainly do this, said Deane, koalas can't because of their different physical shape. They simply can't reach. And yet, they still have very clean pouches during the breeding season.
The researchers have been analysing proteins collected by washing out koala pouches. They know the mix of proteins has antimicrobial activity, but they don't know which protein is responsible.
In the first experiment of its kind, Deane's team is in the process of separating the proteins and identifying their amino acids sequences to see if they are similar to any other known mammalian antimicrobial proteins.
But so far, none of the proteins they have sequenced have been matched to known antimicrobial proteins. This may be because they haven't yet identified the antimicrobial protein, or because the protein responsible is new and unique.
After Deane and team get the full sequence of each protein, they will also model its structure and test it for microbial activity, hoping one day they might even find a new antimicrobial for human use.
But this would be a long way off. Each pouch wash, using just one millilitre of water, yields a miniscule amount of protein mix and so collecting enough for analysis is a painstaking process.
"We had to collect three years of washes to get the sequence data we have at the moment," said Deane.