The study revealed the mechanism by which microbiota contributes to the ability of the manatee (peixe-boi) to obtain energy exclusively from plant food. As Brazil's largest freshwater mammal, it maintains a weight of almost half a ton, feeding only on plants, and the secret lies in its gut.
Mapping the microbiota of the Amazonian manatee (Trichechus inunguis), scientists discovered a previously unknown metabolic pathway: the animal possesses bacteria capable of breaking down epilactose—a carbohydrate that most known microorganisms cannot digest.
This discovery is part of a broader study that demonstrated the great diversity of microorganisms, genes, and enzymes associated with these animals' assimilation of a plant-based diet. In addition to the freshwater species, the research also examined the gut microbiota of the sea manatee (Trichechus manatus). The results, published on Tuesday (11/02) in the journal Nature Microbiology, have significant potential for biotechnological applications.
Mario Murakami, director of the National Laboratory of Bio-renewable Resources at the National Center for Energy and Materials Research (LNBr-CNPEM) and coordinator of the study supported by FAPESP, noted: 'The Amazonian manatee feeds on a large quantity and variety of plants. This diet is subject to seasonal changes, transitioning from the dry season to the wet season. Therefore, throughout its evolution, they have developed an arsenal of gut microorganisms capable of digesting cellulose with exceptional efficiency, about 80% to 86%.'
Thanks to this ability, the ecosystem of bacteria, archaea, viruses, and fungi in the manatee's gut was a natural target for Murakami's group, which had previously studied the gut microbiome of the capybara (Hydrochoerus hydrochaeris), a semi-aquatic species.
Murakami explains the difference in digestion strategy: 'In ruminants, such as cattle, microbial fermentation occurs mainly in the stomach, in the rumen, where microorganisms begin to break down plant biomass. Manatees and capybaras use a different strategy: they are hindgut fermenters, and most of this process occurs after the stomach. Therefore, the microorganisms living in the intestine play a fundamental role in utilizing the high-fiber plant diet.'
The study analyzed samples from 47 animals: 36 Amazonian manatees housed at the Laboratory of Aquatic Mammals of the National Institute of Amazonian Research (INPA) in Manaus, and eleven sea manatees undergoing rehabilitation in the Aquasis NGO Marine Mammal Program in Ceará.
Murakami personally participated in all phases of the research conducted and even dove into the sea to collect a sample. He recounted: 'There was a sea manatee that had already been reintroduced into nature but continued to frequently visit the area near the enclosure where other animals were recovering. By chance, while we were there, it defecated, and the opportunity arose to collect a sample from this animal. I did not hesitate: I jumped into the water to get it.'
Of more than 6 thousand genomes of bacteria and other microorganisms sequenced in the analyses, more than half represent species that have not yet been described by science. Regarding viruses associated with these microbial communities, about 80% were unknown.
Thousands of genes and enzymes that can be used in various biotechnological applications were also discovered. Murakami notes: 'It was difficult to choose where to delve into biochemically. Now we have data for analysis for at least the next ten years.'
One of the main achievements of the study was the discovery of a previously unknown enzyme used by the newly discovered bacterium 'Candidatus Epilactovorans intestinalis' to break down epilactose. Since this sugar is unavailable to the vast majority of microorganisms, this ability serves as an adaptive advantage in the competition for nutrients in the gut. In the future, this mechanism may inspire the creation of new prebiotic agents—ingredients that serve as 'food' to stimulate the growth of beneficial bacteria in our own gut flora.
When comparing the genome of this bacterium with others available in public databases, researchers found a similar sequence originating from the gut microbiota of the Hadza people, one of the last hunter-gatherer groups in Africa, whose slightly over a thousand inhabitants live in northern Tanzania.
According to Murakami, this genetic similarity is not a coincidence. He suggests that the ability to metabolize epilactose may be a hereditary trait of the common ancestor of all mammals. One hypothesis is that the traditional diet of the Hadza people continues to provide the necessary nutrients to sustain this bacterium.
In another aspect, the study showed that manatee microorganisms work together to digest the hardest and most fibrous parts of plants, such as cellulose and hemicellulose. These bacteria combine various strategies to 'deconstruct' the plant cell wall, turning rigid structures into nutrients that the animal can absorb.
Some of these metabolized compounds are produced from lignin—the substance that gives rigidity to plants and represents one of the main obstacles to the industrial use of plant biomass. This set of microorganisms and enzymes could open up new biotechnological solutions for processing agricultural waste and developing bioproducts, including applications in bioenergy, agriculture, and other sectors of the bioeconomy.
Some of the enzymes identified in the study and involved in the deconstruction of plant biomass can also be evaluated for use in platforms such as the Brazilian Enzymatic Cocktail (Coquetel Enzimático Brasileiro, OpEn), developed at CNPEM and customized for processing various raw materials and waste.
Murakami concludes: 'Our enzymatic cocktail has great potential to reduce Brazil's dependence on imported enzymes, as well as to create opportunities for the emergence of new biological industries. This work shows that Brazilian biodiversity is a repository of solutions for global problems and can lead the country to the forefront of the sustainable development race.'
The first authors of the work are Gabriela Persinioti, who coordinates the project supported by FAPESP at CNPEM, and Marcelo Martins, who received a postdoctoral fellowship from the Foundation.
