Hexbyte Glen Cove This is your gut on sushi

Hexbyte Glen Cove

Credit: Jake Dwyer, Michigan Medicine

The next time you get a craving for sushi rolls, you may feel a renewed appreciation for the ocean. It’s to thank not only for your fish and seaweed wrapper, but, as a new Michigan Medicine study suggests, for the bacteria in your gut that digest seaweed.

The ocean is one of the largest reservoirs of carbon on the planet, much of it locked inside seaweed. Marine bacteria play a critical role in the carbon cycle by breaking down seaweed. A little over a decade ago, researchers found the that enable ocean bacteria to degrade the complex carbohydrate known as porphyran, found in cold-water seaweed, in a microbiome sample from a Japanese adult.

A new study, led by Nicolas Pudlo, Ph.D., Gabriel Vasconcelos Pereira, Ph.D., and Eric Martens, Ph.D., of the U-M Medical School, has found that these genes of oceanic origin are more common than previously recognized, entering the human gut microbiome through a process known as lateral gene-transfer.

During digestion, gut bacteria in humans break down dietary fiber, or , found in fruits, vegetables, and grains. However, the polysaccharides found in seaweed have different chemical structures than land-sourced foods. Somehow, genes from the ocean-dwelling Bacteroidetes—a genus of bacteria that is a key player in the microbiome—found their way into the human gut.

“Whether they came directly from an oceanic bacterium someone just happened to consume or through a more complex path into the human gut is still a mystery,” said Martens, a professor in the Department of Microbiology and Immunology.

To examine just how extensive the seaweed gene clusters are in gut Bacteroidetes, the team turned to an unusual source: stool samples from U-M undergraduate students.

“We received the samples in small glass tubes and did all of our culturing within the lab’s anaerobic chamber,” commented Ahmed Ali, one of the student researchers on the study. “I remember working in the chamber was hot and somewhat difficult, but this was definitely offset by the fact that we did not have to ‘smell the scientific process’ at work,” he quipped.

They then analyzed the bacteria’s ability to degrade several seaweed-derived polysaccharides, including porphyran, laminarin, alginate and carrageenan.

The team found that genes for processing laminarin were broadly represented in the samples, possibly linked to the related ability to process beta-glucans, sugars also found in oats and whole grains. Yet, the other seaweed polysaccharides were used by fewer bacterial species and present in fewer samples.

“The genes to process agarose and porphyran, two of the more commonly consumed seaweeds in Southeast Asia, tended to be enriched in the people living there,” said Martens. Taking a closer look at the geographic distribution of the gene clusters, the team referenced genomic surveys from samples taken from more than 2000 people in Asia, Africa, North and South America, and Europe.

The genes for degrading porphyran were indeed enriched in samples from China and Japan. Genes for processing carrageenan, consumed since 400 B.C in China, and now widely used as a food additive in everything from oat milk to infant formula in the United States, were also enriched in samples from China, Japan and North America.

Adding further intrigue to the evolution of seaweed digestion, the team fortuitously discovered that the bacteria Firmicutes, which are even more prevalent in the human gut than Bacteroidetes, also have picked up the genetic ability to grow on polysaccharides.

“Firmicutes are known to live in fish intestines and the closest ancestors of the genes that appear to have jumped into human gut Firmicutes were ones found in fish,” said Martens.

The study, notes the team, opens new questions about the complex interplay between diet and the adaptation of the in populations around the world.

Additional authors on the paper include Jaagni Parnami, Melissa Cid, Stephanie Markert, Jeffrey P. Tingley, Frank Unfried, Austin Campbell, Karthik Urs, Yao Xiao, Ryan Adams, Duña Martin, David N. Bolam, Dörte Becher, Thomas M. Schmidt, Wade Abbott, Thomas Schweder and Jan Hendrik Hehemann.



More information:
Nicholas A. Pudlo et al, Diverse events have transferred genes for edible seaweed digestion from marine to human gut bacteria, Cell Host & Microbe (2022). DOI: 10.1016/j.chom.2022.02.001

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Hexbyte Glen Cove Study finds nearly 500 ancient ceremonial sites in southern Mexico

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

A team of international researchers led by the University of Arizona reported last year that they had uncovered the largest and oldest Maya monument—Aguada Fénix. That same team has now uncovered nearly 500 smaller ceremonial complexes that are similar in shape and features to Aguada Fénix. The find transforms previous understanding of Mesoamerican civilization origins and the relationship between the Olmec and the Maya people.

The team’s findings are detailed in a new paper published in the journal Nature Human Behavior. UArizona anthropology professor Takeshi Inomata is the paper’s first author. His UArizona coauthors include anthropology professor Daniela Triadan and Accelerator Mass Spectrometry Lab director Greg Hodgins.

Using data gathered through an airborne laser mapping technique called lidar, the researchers identified 478 complexes in the Mexican states of Tabasco and Veracruz. Lidar penetrates the tree canopy and reflects three-dimensional forms of archaeological features hidden under vegetation. The lidar data was collected by the Mexican governmental organization Instituto Nacional de Estadística y Geografía and covered a 32,800-square-mile area, which is about the same size as the island of Ireland.

Publicly available lidar data allows researchers to study huge areas before they follow up with high-resolution lidar to study sites of interest in greater detail.

“It was unthinkable to study an area this large until a few years ago,” Inomata said. “Publicly available lidar is transforming archaeology.”

Missing Links?

There’s a longstanding debate over whether the Olmec civilization led to the development of the Maya civilization or if the Maya developed independently.

The newly uncovered sites are located in a broad area encompassing the Olmec region and the western Maya lowlands. The complexes were likely constructed between 1100 B.C. and 400 B.C. and were built by diverse groups nearly a millennium before the heyday of the Maya civilization between A.D. 250 and 950.

The researchers found that the complexes share similar features with the earliest center in the Olmec area, San Lorenzo, which peaked between 1400 and 1100 BC. Aguada Fenix in the Maya area and other related sites began to adopt San Lorenzo’s form and formalize it around 1100 BC.

At San Lorenzo, the team also found a previously unrecognized rectangular space.

“The sites are big horizontally but not vertically,” Inomata said. “People will be walking on one and won’t notice its rectangular space, but we can see it with lidar really nicely.”

The researchers’ work suggests that San Lorenzo served as a template for later constructions, including Aguada Fénix.

“People always thought San Lorenzo was very unique and different from what came later in terms of site arrangement,” Inomata said. “But now we show that San Lorenzo is very similar to Aguada Fénix—it has a rectangular plaza flanked by edge platforms. Those features become very clear in lidar and are also found at Aguada Fénix, which was built a little bit later. This tells us that San Lorenzo is very important for the beginning of some of these ideas that were later used by the Maya.”

Sites Were Likely Ritual Spaces

The sites uncovered by Inomata and his collaborators were likely used as ritual gathering sites, according to the paper. They include large central open spaces where lots of people could gather and participate in rituals.

The researchers also analyzed each site’s orientation and found that the sites seem to be aligned to the sunrise of a certain date, when possible.

“There are lots of exceptions; for example, not every site has enough space to place the rectangular form in a desired direction, but when they can, they seem to have chosen certain dates,” Inomata said.

While it’s not clear why the specific dates were chosen, one possibility is that they may be tied to Zenith passage day, which is when the sun passes directly overhead. This occurs on May 10 in the region where the sites were found. This day marks the beginning of the rainy season and the planting of maize. Some groups chose to orient their sites to the directions of the sunrise on days 40, 60, 80 or 100 days before the zenith passage day. This is significant because the later Mesoamerican calendars are based on the number 20.

San Lorenzo, Aguada Fénix and some other sites have 20 edge platforms along the eastern and western sides of the rectangular plaza. Edge platforms are mounds placed along the edges of the large rectangular plazas. They define the shape of the plazas, and each are usually no taller than about 3 feet.

“This means that they were representing cosmological ideas through these ceremonial spaces,” Inomata said. “In this space, people gathered according to this ceremonial calendar.”

Inomata stressed that this is just the beginning of the team’s work.

“There are still lots of unanswered questions,” he said.

Researchers wonder what the social organization of the people who built the complexes looked like. San Lorenzo possibly had rulers, which is suggested by sculptures.

“But Aguada Fénix doesn’t have those things,” Inomata said. “We think that people were still somehow mobile, because they had just begun to use ceramics and lived in ephemeral structures on the ground level. People were in transition to more settled lifeways, and many of those areas probably didn’t have much hierarchical organization. But still, they could make this kind of very well-organized center.”

Inomata’s team and others are still searching for more evidence to explain these differences in social organization.

“Continuing to excavate the sites to find these answers will take much longer,” Inomata said, “and will involve many other scholars.”



More information:
Takeshi Inomata, Origins and spread of formal ceremonial complexes in the Olmec and Maya regions revealed by airborne lidar, Nature Human Beh

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