A diverse range of so-called "friendly" bacteria live within each human body and can be considered an ecosystem in their own right. A new article published in Genome Biology shows that the make-up of this bacterial ecosystem is unique to each individual and that living with someone does not cause your sets of bacteria to become alike.

The study, which was performed by Rob Knight's group at the University of Colorado, also demonstrates that different parts of the body – even your right and left palms – are home to different sets of bacteria and that the bacterial species in your body change on a day-to-day basis. In fact, much as you might expect in an ecosystem, some species of bacteria were observed to "bloom" by going through cycles of brief periods of high abundance followed by longer periods in which their population was small. George Weinstock, who is a leader of the Human Microbiome Project, summarizes the observed microbial ecosystem as "volatile" in an accompanying Research Highlight also appearing in Genome Biology's latest issue.

The Genome Biology study is only now possible because recent technological breakthroughs have allowed the nature of these bacterial ecosystems to be studied in unprecedented detail. This technology will also enable researchers to design follow-up experiments seeking to answer important questions such as what effect antibiotics or diet have on "friendly" bacteria and how the bacterial ecosystem contributes to diseases of the gut, such as Irritable Bowel Syndrome and Crohn's disease.