Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans

Authors: MORAIS, SARAH - Ben Gurion University Of Negev; WINKLER, SARAH - Ben Gurion University Of Negev; ZOREA, ALVAH - Ben Gurion University Of Negev; LEVIN, LIRON - Ben Gurion University Of Negev; NAGIES, FALK - Heinrich-Heine University; KAPUST, NILS - Heinrich-Heine University; SETTER-LAMED, EVA - Weizmann Institite Of Science; ARTAN-FURMAN, AVITAL - Weizmann Institite Of Science; BOLAM, DAVID - Newcastle University; Yadav, Madhav; BAYER, EDWARD - Weizmann Institite Of Science; MARTIN, WILLIAM - Heinrich-Heine University; MIZRAHI, ITZHAK - Ben Gurion University Of Negev

Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2024
Publication Date: 3/15/2024
Citation: Morais, S., Winkler, S., Zorea, A., Levin, L., Nagies, F.S., Kapust, N., Setter-Lamed, E., Artan-Furman, A., Bolam, D.N., Yadav, M.P., Bayer, E.A., Martin, W.F., Mizrahi, I. 2024. Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans. Science. https://doi.org/10.1126/science.adj9223.
DOI: https://doi.org/10.1126/science.adj9223

Interpretive Summary: The human gut microbiota plays a key role in human physiology and health. Plant fibers are major nutrients for the growth of beneficial bacteria in the human gut. Humans, like all mammals, depend on the gut microbiome for digestion of cellulose, the main component of plant fiber. But evidence for cellulose fermentation in the human gut is rare. We have discovered bacteria that degrade plant derived complex carbohydrates in the human gut. These bacteria may be originated from the guts of animals and evolved to adapt to the humans through a genetic mechanism. They are abundant and widespread among human hunter-gatherer and rural populations. But they are rare in the people of industrialized societies, which may be due to lifestyle differences. This indicates that the people of industrialized societies lack the bacteria, which ferment cellulose in their gut. This study shows that strains of these bacteria may be reintroduced to the human gut microbiome by dietary changes. Evidence for the importance of plant fibers for initiating the growth of the useful bacteria in the human gut will benefit and fiber crop processors and thereby producers.

Technical Abstract: Humans, like all mammals, depend on the gut microbiome for digestion of cellulose, the main component of plant fiber, but evidence for cellulose fermentation in the human gut is scarce. We have identified new ruminococcal species that assemble functional cellulosomes and degrade plant cell wall polysaccharides as gut microbiome inhabitants of some human populations. These species likely originated from either the primate or ruminant gut and evolved to adapt to the human gut through gene acquisition from other microbes. They are abundant and widespread among human hunter-gatherer and rural populations, but are extremely rare in populations from industrialized societies, indicating extinction in response to the lifestyle of the industrialized societies. The disappearance of the identified species accounts for the scarcity of cellulose fermentation in the human gut microbiota, suggesting that dietary change and reintroduction may restore fiber digestion where the trait is lacking.