Obesity could spread from person to person in a similar way to the contagious bug, C.difficile, a new study has suggested.
A growing body of evidence has placed increasing importance on the balance of bacteria in our gut.
Imbalances in the gut microbiome can contribute to a number of complex conditions, including obesity, inflammatory bowel disease, irritable bowel syndrome and allergies, studies have shown.
But, for the first time, scientists believe traces of the bacteria can survive outside the body, raising the possibility that it could be ingested.
If that bacteria disrupts a person's gut microbiome in a negative way, it is possible, the researchers say, for these complex diseases to manifest themselves.
A new study of the gut microbiota has suggested obesity, inflammatory bowel disease, IBS and allergies could be contagious, spreading from person to person via spores of bacteria that can survive in the open air
A team from the Wellcome Trust Sanger Institute turned their attention to the proportion of bacteria that form spores within the gut.
Spores are a form of bacterial hibernation, that allows some bacteria to remain dormant for long periods of time.
Researchers from the Wellcome Trust Sanger Institute discovered approximately one third of the gut microbiota from a healthy person produced spores that allow bacteria to survive in open air and potentially move between people.
They said this provides a means of microbiota transmission that has not been considered before.
And, furthermore, the authors suggest it could imply that health and certain diseases could be passed, not just through human genetics, but also via the microbiome.
Dr Trevor Lawley, group leader at the Sanger Institute, said: 'Being able to cast light on this microbial "dark matter" has implications for the whole of biology and how we consider health.
'We will be able to isolate the microbes from people with a specific disease, such as infection, cancers or autoimmune diseases, and study these microbes in a mouse model to see what happens.
'Studying our "second" genome, that of the microbiota, will lead to a huge increase in our understanding of basic biology and the relationship between our gut bacteria and health and disease.'
This research will allow scientists to start to create tailor-made treatment with specific beneficial bacteria, they said.
Research in this field has expanded greatly in recent years, with the intestinal microbiome being labeled the 'forgotten organ', such is its importance to human health.
Around two per cent of a person's body weight is linked to bacteria.
Many of these bacteria are sensitive to oxygen and are difficult to culture in the laboratory, so until now it has been very difficult to isolate and study them.
Hilary Browne from the Sanger Institute, explained: 'It has become increasingly evident that microbial communities play a large role in human health and disease.
Imbalances in the gut microbiome can contribute to a number of complex conditions, including obesity, inflammatory bowel disease, irritable bowel syndrome and allergies, studies have shown. But, for the first time, scientists believe traces of the bacteria can survive outside the body, raising the possibility that it could be ingested and disrupt a person's microbiome, triggering obesity and other chronic diseases
'By developing a new process to isolate gastrointestinal bacteria, we were able to sequence their genomes to understand more about their biology.
'We can also store them for long periods of time making them available for further research.'
Antibiotics wipe out our gut bacteria - killing both the pathogen targets and the beneficial bacteria too.
There is then the potential for less desirable bacteria, such as those with antibiotic resistance, to repopulate the gut faster than the beneficial bacteria, leading to further health issues, such as Clostridium difficile infection.
Current treatment for C. difficile infection can involve transplants of faeces from healthy people, to repopulate the gut.
However this treatment is far from ideal.
Using the library of new bacteria, Dr Lawley and his team are hoping to create a pill, containing a rationally selected, defined mix of bacteria, which could be taken by patients and replace faecal transplants.
Dr Sam Forster from the Sanger Institute and Hudson Institute of Medical Research in Australia said: 'The extensive database of genomes we have generated from these bacteria is also essential for studying which bacteria are present or absent in people with gastrointestinal conditions.
'Now we can start to design mixtures of therapeutics candidates for use in these diseases.'
The findings are published in Nature.