evolution: symbiosis with many good bacteria (Introduction)

by David Turell , Wednesday, November 22, 2023, 18:59 (157 days ago) @ David Turell

Can influence animal behavior:

https://phys.org/news/2023-11-bacteria-contribute-modulation-animal-behavior.html

In recent years, researchers have gathered growing evidence that the composition and balance of the microbiome plays a decisive role in the function and health of the organism as a whole.

They have identified a fundamentally important aspect of these functional relationships in the communication between nerve cells of the host and its microbiome, which was first established very early in evolution. The significance of this cooperation and how these interactions affect behavior is still largely unknown.

a research team from the Collaborative Research Center (CRC) 1182 "Origin and Function of Metaorganisms" at Kiel University has gained new insights into the cooperation between the nervous system and the microbiome. Using the freshwater polyp Hydra as an example, the Kiel researchers investigated the neuronal basis of their feeding behavior and whether and in what way the microbiome intervenes in this behavior.

In doing so, they were able to prove mechanistically for the first time that a microbiome with reduced diversity affects the function of certain nerve cells and thus alters the feeding behavior. They published their research results today in the journal Current Biology.

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"Underlying the feeding behavior is a neuronal control that is significantly more complex than was previously assumed from the simple nerve network of Hydra," Giez continues. Using a calcium-based visualization method, the research team was able to observe the nerve populations involved in feeding behavior in real-time in the living animal and thus identify the neuronal circuit involved.

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In order to find out which bacteria have a particularly significant influence, the Kiel researchers first colonized germ-free animals with one defined bacterial species each in the next step. "A particularly interesting effect was seen when colonizing with the bacterium Curvibacter. The feeding behavior of animals colonized only with Curvibacter is very strongly impaired: These animals can only open their mouths to a very limited extent," Giez continues.

In further studies, Curvibacter was found to produce the amino acid glutamate, which also plays an important role in human metabolism. When the microbiome is greatly reduced in composition and only Curvibacter is present, glutamate accumulates, binds to neurons, and leads to a blockage of the mouth opening. The inhibitory effect of the Curvibacter bacteria is reversed as soon as the remaining members of the microbiome are also reintroduced to the tissue.

"Overall, we were able to prove that even in phylogenetically ancient animals, a diverse microbiome is necessary for normal feeding behavior. If the composition of this microbiome is severely disturbed, significant changes in behavior occur," says Professor Thomas Bosch, head of the Cell and Developmental Biology group.

The researchers have gathered evidence that this is due to interactions between the different members of the microbiome. If there is a species-rich, "normal" microbiome, the glutamate produced is taken up and utilized by other bacterial species, and the neuronal circuit responsible for feeding behavior is not disturbed.

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"Our study opens the door for further research into the effects of the interplay between the microbiome and the nervous system on the functions of the whole organism. Among other things, we want to find out in the future whether and how microorganisms are already involved in the formation of the nervous system during embryonic development and what part the microbiome plays in the production of neurotransmitters," Bosch says.

Comment: constant contact with bacteria is part of life on Earth. Most of the contact is important to all living functions.