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'Fuzzy' Bacterial Boundaries

A paper published in Nature last year suggested that human gut bacterial communities fall into three distinct enterotypes, and that each enterotype is characterized by high levels of a single microbial genus — Bacteroides, Prevotella, or Ruminococcus — says Ed Yong at Nature News. But at the International Human Microbiome Congress in Paris this week, some researchers are saying those enterotypic boundaries may be "fuzzier" than previously suggested, he says. A new study, as yet unpublished, "shows that a genus of archaea called Methanobrevibacter joins Ruminococcus as a defining microbe in the third enterotype," Yong adds. "And the separation between this cluster and the Bacteroides-led enterotype is no longer as clear, although these two groups remain distinct from the Prevotella-driven one." University of Colorado at Boulder computational biologist Dan Knights told conference attendees that discrete enterotypes may not exist at all.

Other researchers disagreed. "This disagreement matters because enterotypes might eventually affect how we weigh a person’s risk of disease, or their response to different drugs," Yong says. "The issue will only be resolved with larger studies that include more populations, such as South Americans and Africans."

The Scan

Tens of Millions Saved

The Associated Press writes that vaccines against COVID-19 saved an estimated 20 million lives in their first year.

Supersized Bacterium

NPR reports that researchers have found and characterized a bacterium that is visible to the naked eye.

Also Subvariants

Moderna says its bivalent SARS-CoV-2 vaccine leads to a strong immune response against Omicron subvariants, the Wall Street Journal reports.

Science Papers Present Gene-Edited Mouse Models of Liver Cancer, Hürthle Cell Carcinoma Analysis

In Science this week: a collection of mouse models of primary liver cancer, and more.