An international team of researchers reports in Nature this week that modern-day European populations house genetic contributions from three groups of ancient Europeans. The team, led by Harvard Medical School's David Reich sequenced ancient genomes belonging to a 7,000-year-old farmer from Germany, an 8,000 year-old hunter-gatherer from Luxembourg, and seven 8,000-year-old hunter-gatherers from Sweden. Through comparing the sequences they generated to other ancient human genomes as well as to 2,345 genomes from contemporary humans, they homed in on three sources of genetic variation in modern humans: western European hunter-gatherers, ancient north Eurasians, and early European farmers. The early European farmers, Reich and his colleagues note, appear to be descended from a basal Eurasian branch that split off from other non-African lineages early on.
Also in Nature, researchers from the US, Australia, and Bangladesh report on their survey of indicator species present in the feces of people suffering and recovering from cholera. They collected fecal samples from 1,153 patients with acute diarrhea as well as from healthy children and adults living in the same region of Bangladesh. Through their time-series metagenomic analysis, the researchers found that a certain bacterium was associated with recovery from disease. In a mouse model of the disease, Ruminococcus obeum numbers consistently went up upon Vibrio cholerae infection and help prevent V. cholerae colonization.