12,000 different viruses in our gut
The researchers, from San Diego State University found that more than half were previously unknown to science.
Most are phages - viruses that infect and kill bacteria - which are perfectly harmless to humans.
Writing in the Journal of Bacteriology, the researchers say their findings could lead to new treatments for gut disorders.
The gut contains up to 500 types of bacteria which play a crucial role in helping to digest food, and regulating our bowels' health.
The researchers say that phages could be used to tweak the balance of these bacteria.
They say: 'Understanding the population structure and dynamics of the normal human intestinal microbiota [micro organisms] has important implications for human health, nutrition, and the development of probiotics for the treatment and prevention of gastrointestinal disorders.'
Only the viruses and bacteria that cause disease have been studied in detail.
Most of the world's bugs cannot be grown in the laboratory - and therefore cannot be identified.
But the San Diego team was able to garner information about them by extracting their genes from samples of human faeces.
The researchers compared the genetic material they discovered with DNA sequences from known bacteria and viruses.
They found matches to families of phages, to previously described bacteria, to tiny organisms called protozoa and to DNA fragments called mobile elements that are shared by bacteria and viruses.
12000 diferite virusuri în intestin - 12,000 different viruses in our gut - articole medicale engleza - startsanatate