Gut flora and the human rainforest
Scientists have known for decades that the human intestinal tract is home to an abundance of diverse bacteria. This microbial rainforest is introduced incrementally to infants as they grow—primarily from their mothers during birth and breastfeeding and from everyday encounters. Many of these microbes aid in digestion and fight off pathogens, but until recently, researchers were not certain if phages, viruses that infect bacteria, were also present in the human gut.
According to a study published today in Nature, phages are indeed part of this jungle, and they are unique to each individual. Alejandro Reyes from the Washington University School of Medicine in St Louis and colleagues sequenced the viral DNA found in fecal samples from four sets of female identical twins and their mothers. Not only were these sequences, called viromes, different from the viromes of strangers, the viromes of identical twins did not even match. This was compared to the bacterial profiles of the identical twins which overlapped by about 50% (significantly more than between strangers).
According to an article in Science Now, “Equally surprising…was the communities’ consistency: the viral makeup changed less than 5% over the course of the year, and the viromes of the most abundant phages changed less than 1%. Rapidly changing viromes would have signaled an ‘arms race’ in which threatened bacteria were adapting to survive phage attacks, and the phages were adapting to avoid bacterial defenses.”
Read more at “A Viral Wonderland in the Human Gut” in Science Now and “People Have Friendly Gut Viruses” in Wired Science. An organized oral session on microbial communities in the human body will be presented at the Ecological Society of America’s 95th Annual Meeting in Pittsburgh from August 1-6.
Photo credit: Claudio.Ar
Reyes, A., Haynes, M., Hanson, N., Angly, F., Heath, A., Rohwer, F., & Gordon, J. (2010). Viruses in the faecal microbiota of monozygotic twins and their mothers Nature, 466 (7304), 334-338 DOI: 10.1038/nature09199