'Super poo donors' wanted
Claudia Campanella, 31, works as a student support administrator at a UK university, and in her spare time she is a poo donor.
"Some of my friends think it is a bit weird or disgusting, but it doesn't worry me. It's very easy to donate and I just want to help with medical research. I'm glad to contribute."
Her faeces, teeming with "good" bugs, will be put into the bowel of a sick patient to help their poorly gut get better.
Claudia knows her donation is extremely useful - that is why she does it - but is her poo extra special?
Scientists believe some people's poo might contain an ideal mix of healing bacteria to fix gut diseases, making them super-donors.
Claudia says she wanted to become a donor because she had read that vegans might make particularly good candidates.
There's no good evidence that vegan poo is better than any other human faeces, but experts are exploring what might make a stool "super".
Dr Justin O'Sullivan is a molecular biology expert at the University of Auckland and he has been investigating the concept of super poo donors.
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Our guts house millions of bugs that live inside us as a community. This diverse microbiome is unique to each us - no two are exactly the same.
Although faecal transplantation is still a relatively new field of medicine, evidence from the studies that have been done hint that some donors make the best poo for the job.
Dr O'Sullivan says: "We see transplants from super-donors achieve clinical remission rates of perhaps double the remaining average.
"Our hope is that if we can discover how this happens, then we can improve the success of faecal transplantation and even trial it for new microbiome-associated conditions like Alzheimer's, multiple sclerosis and asthma."
Dr Jon Landy is a consultant gastroenterologist for West Hertfordshire Hospitals NHS Trust and helps to co-ordinate their faecal transplant unit.
He agrees with the idea of a super-donor, but says finding one could be tricky.
"We do not understand yet what makes a super-donor, or why," he said.
"We always make sure our donors are healthy and not carrying any disease, but we don't test all of their microbiome to see what that is like.
"These are the sorts of investigations that might need to be done."
Dr O'Sullivan's research, published in the journal Frontiers in Cellular and Infection Microbiology, suggests having lots of different microorganisms in your poo might be the advantage.
He says a larger number of species in the donor's stool has been shown to be one of the most significant factors influencing faecal transplantation outcome. And patients who respond well to the transplants develop a more diverse microbiome too.
But studies suggest success could also depend on how good a match the donor is for the patient.
And it might not only be which bacteria are present in the poo.
"Some cases of recurrent diarrheal infection have even been cured with transplants of filtered stool, that has had all the live bacteria filtered out but still contains DNA, viruses and other debris.
"These viruses could affect the survival and metabolic function of transplanted bacteria and other microbes," says Dr O'Sullivan.
Dr Julie McDonald, a microbiome expert at Imperial College London, has been studying how to boost the success rate of stool transplants.
Currently, most donations are used to treat a dangerous bowel condition caused by an infection called clostridium difficile.
This infection can take hold when a patient's own "good" bowel bugs have been wiped out by antibiotics. For the most vulnerable, it can be deadly.
Dr McDonald's work suggests poo transplants do a very specific job, replacing something lost in disease.
She found patients suffering from clostridium difficile infections had virtually undetectable levels of a short-chain fatty acid valerate produced by healthy gut microbial metabolism
The levels could only be restored with a successful faecal transplant.
"In our lab we are trying to figure out exactly how the transplants work and we are looking at whether we even move away from giving faeces itself."
Instead of giving the patient an injection of faeces they would be given a treatment based on the faeces, which they might find less off-putting.
This might help get round the whole poo taboo that's associated with donating, she says.
Claudia wants people to "get over the mental barrier" and think about becoming a donor.
"It's really very easy to donate. It's simple to do. If you are thinking about it, check if a hospital nearby has a service and get in touch with them.
"I collect my fresh sample at home in a container that my hospital provides. Then I drop it off to the hospital as I pass by it on my way to work. It's just a little bit of effort."
Claudia's now thinking about becoming a blood donor too. "I've not got round to that yet, but it's something I might do."