There is competition in nature and the fittest survive. Or at least that’s what we’ve heard a lot. However, the planet is much more complicated than that because we earthlings have relationships with other species on levels that we often do not realize. As Lynn Margulis and Dorion Sagan once said, one must understand how organisms come together in new and fascinating ways to understand the true complexities of life.
This is what the holobiont is all about, a concept that refers to an entity formed by the union of different species that become an ecological entity. In other words, if an animal or plant (host) lives in symbiosis with the microorganisms it harbors (hosts or symbionts), it is a holobiont. Something like a group of merged beings or a multi-species complex.
More information
Scott F. Gilbert, evolutionary biologist, Howard A. Schneiderman Professor Emeritus at Swarthmore College and Distinguished Professor Emeritus at the University of Helsinki, explains it this way: “All organisms appear to be holobionts, and we are not just made up of cells derived from the zygote , but also by symbiotic bacteria, fungi and viruses. Each animal is a biome, a series of interactive ecosystems. Also, these symbiotic microbes don’t just travel with us. They help to build our body, regulate our metabolic processes and build up our defenses. This has many implications for the way we see life.”
All organisms appear to be holobionts and we are also made up of symbiotic bacteria, fungi and viruses. Each animal is a biome, a series of interactive ecosystems
Scott F. Gilbert, Evolutionary Developmental Biologist, Professor Emeritus at Swarthmore College
In fact, our bond with microorganisms is so deep that we become the ecosystem in which they live while influencing our development, health and even behavior.
For Cristina Dorador, a microbial ecologist and academic at the University of Antofagasta, “The holobiont invites us to think on different scales. It seems that the microscopic and the immense don’t converse, but in fact they do.” This has been revealed by technological advances. “The big step came in the 2010s with massive DNA sequencing techniques because complete microbial groups invisible to classical techniques were discovered. Furthermore, the Human Microbiome Project revealed the microbial diversity in the human body and debunked some of the theories that existed at the time,” he adds.
microbial human
Perhaps the best-known example is the gut microbiota, the community of microorganisms that allows us to break down food and is key to our immune system.
“Anatomically, about half of the cells in the human body are microbial. Also, each microbial species is not associated with us by accident, but is found in specific locations. We get these microbes when we pass through the birth canal. They are parting gifts from our mother. These microbes colonize our bodies, particularly our gut, and help stop our development,” Gilbert explains.
Not surprisingly, microbes also play a role in diseases ranging from depression to cancer. In fact, tumors have an associated microbiome, and the presence of these microorganisms would explain why some people are more sensitive to immunotherapy.
In another area, there are studies showing that replacing bacteria in the gut would help reduce autistic behaviors in rats. Dorador, who was involved in research into autism and microbiota, says: “It has been reported that around 40% of people on the autism spectrum have gastrointestinal problems. It was found that there is an accumulation of certain groups of bacteria. We wanted to find a model to explain whether this change at the microbial level, which we don’t know how occurs, produces metabolites or products that alter neuronal function in some way.” Clearly, there is still much to be unraveled.
For Scott Gilbert, “we are all lichens” because we are not so different from these beings, which were formed by the union of a fungus with algae and cyanobacteria that we can see in trees, rocks, and other habitats, among other things. Paula Diaz Levi
Team more than individual
Among other things, the holobiont generates new morphological, physiological and immunological characteristics that do not exist separately in the species.
Entomologist Constanza Schapheer’s favorite example is insects that recycle nutrients, such as termites. “These animals harbor microorganisms such as bacteria and protists in their digestive systems, which help the termite absorb nutrients it otherwise would not be able to absorb. The acquisition of gut symbionts was key to the evolution of these insects. There are many similar examples in nature, the most paradigmatic being lichens and corals,” says the fellow postdoctoral researcher at the Faculty of Agricultural Sciences at the University of Chile.
Cows, on the other hand, eat grass, but their genome doesn’t produce enzymes capable of digesting cellulose or other compounds in their feed. The good news (for them) is that their symbiotic microbes residing in their rumen are responsible for processing what these mammals can’t.
What we think of as an “organism” is actually a set of integrated organisms. For this reason, scientists and philosophers question the existence of the “individual” as we commonly understand it.
In addition, some change as they acquire new microorganisms. The American biologist cites the red turpentine beetle as an example: “It is a small pest in the United States, where its symbiotic fungi dig holes in damaged trees. However, when it was accidentally exported to China, the beetle acquired a new set of fungal symbionts that enabled it to bore holes in healthy trees and kill them.
In other words, what we think of as an “organism” would actually be a set of integrated organisms. For this reason, scientists and philosophers like Gilbert and his colleagues have questioned the existence of the “individual” as we commonly understand it.
“We evolved to anticipate these symbiotic microbes and their signals. So each of us functions as a community or as a team. We are individuals only to the extent that one community differs from another community or one team from another team. I’m Team Scott Gilbert,” emphasizes the scientist, who also contributed to the book “Microhabitable”.
Its meaning in nature
Understanding ourselves as holobionts has implications not only for our health but also for the environment.
Humans tend to maintain species or ecosystems separately without concern for maintaining the relationships and cycles that sustain organisms as a whole. A forest or desert cannot survive without the connections its macro and micro dwellers weave.
This inspired Schapheer and other colleagues to propose the concept of the “ecosystem holobiont,” which refers to a holobiont performing key ecological processes to protect nature.
We call this phenomenon an emergent property, it occurs thanks to a holobiont and is part of a key ecosystem process. Our planet has its conditions thanks to these processes, it is vital to preserve them
Constanza Schapheer, Entomologist, Agricultural Sciences from the University of Chile
Let’s get back to the living things that decompose organic matter, a fundamental task to have healthy soils that support agriculture, for example. If the breakdown of this matter were only done by microorganisms, it would be very slow (due to their tiny size), but if they have a larger partner – like an insect – they will make the process faster and easier together. This is because the animal that houses them in its digestive tract has better mobility and has mouthparts to break up the material.
Schapheer explains: “We call this phenomenon an emergent property, when this property occurs thanks to a holobiont and is part of a key ecosystem process, we speak of an ecosystem holobiont. One of the reasons our planet has the conditions it has is thanks to these processes that are vital to sustaining.”
Climate change can also trigger the breakdown of symbiotic relationships, as is the case with coral bleaching, which occurs when these animals lose their symbiotic microalgae. Picasa
We are diversity
Health crises, biodiversity loss and climate change are some of the major problems we are currently facing. The multiple consequences include the breakdown of symbiotic relationships, such as soil degradation that robs plants of their symbiotic fungi and bacteria, or rises in sea temperature that stress corals, which in response expel their microalgae and trigger bleaching.
Likewise, overuse of biocides (like antibiotics or disinfectants) kills microbes that we evolved with.
Gilbert emphasizes that “being a holobiont means that we are products of our environment in ways we never imagined before. Healthy people need a healthy environment. That means the environment needs to be healthy for the microbes we need for our bodies to function, as well as the microbes that help make the plants we eat.”
For this reason, “holobiontic thinking” could contribute both to understanding the phenomena and to possible solutions.
“For the preservation of species, rather than preserving the individual, we should focus on preserving functional units, that is, the set of beings that make up the holobiont. That way, organisms and ecosystem processes would be taken into account to keep the planet functioning,” says Schapheer.
But there is also a lesson in humility for Dorador: “We are an ecosystem where it is also important to share and collaborate. The massive symbiosis that exists on the planet and the holobionts opens up ways to understand complex problems and helps us to position ourselves from diversity.”
you can follow THEME on Facebook, Twitter and Instagram, or sign up here to receive our weekly newsletter.
Subscribe to continue reading
Read without limits