Bacteria in mushrooms provide evidence of the origins of complex life

Bacteria in mushrooms provide evidence of the origins of complex life

scientists who use a tiny hollow needle and a bicycle pump have managed to plant bacteria into a larger cell. This creates a relationship that resembles those who have initiated the evolution of complex life.

This performance, which was published in the journal Nature on October 2, 1 could help researchers that understand the origins of more than one more than one Billion years to the emergence of specialized organelles such as mitochondria and chloroplasts.

endosymbionic relationships in which a microbacterial partner live harmoniously in the cells of another organism can be found in numerous forms of life, including insects and fungi. Scientists believe that mitochondria - the organelles that are responsible for energy production in cells - were created as a bacterium found refuge in an ancestor of the eukaryotic cells. Chloroplasts were created when the ancestor of the plants recorded a photo -ynthical microorganism.

The determination of the factors that have formed and maintained these connections is difficult because they are so long ago. To avoid this problem, a team under the direction of microbiologist Julia Vorholt has developed endosymbiotic relationships in the laboratory in recent years at the Federal Institute of Technology in Zurich (ETH Zurich). Your approach uses a 500-1000 nanometer wide needle to pierce host cells and then insert bacterial cells individually.

The first attempts often failed; One reason for this was that the potential symbion was shared too quickly and killed his landlord 2 . The team was more successful than a natural symbiosis between some tribes of the fungal plant pathogen rhizopus microsporus and the bacterium Mycetohabitan's rhizoxinica recovered that produces a toxin that protects the fungus from predate

The introduction of bacterial cells into the mushrooms, however, was a challenge because they have thick cell walls that maintain a high internal pressure. After the wall was pierced with the needle, the researchers used a bicycle pump - later a compressor - to maintain enough pressure to introduce the bacteria.

After the initial shock of the "operation", the mushrooms continued their life cycles and produced spores, some of which contained bacteria. When these spores sprouted, bacteria were also available in the cells of the next generation of fungi. This showed that the new endosymbiosis was transferable to the offspring - a crucial finding.

However, the bacterial spores were low. In a mixed population of spores (some with bacteria and some without), the bacteria -containing disappeared after two generations. In order to improve relationships, the researchers used a fluorescent cell sorter to select spores that contained bacteria - which had been marked with a shining protein - and only propagated these spores in future reproductive rounds. After ten generations, the bacteria-containing spores sprouted almost as efficiently as those without bacteria.

The basis for this adaptation is not clear. Genom sequencing identified some mutations that were associated with the improved germination success in the mushroom - a tribe of R. Microsporus, which is not known to wear endosymbions - and found no changes in the bacteria.

The line that was most efficiently germinated seemed to limit the number of bacteria in every spore, says Gabriel Giger, co -author of the study and microbiologist at ETH Zurich. "There are opportunities for these two partners to live better and easier. This is something that is very important for us."

The researchers don't know much about the mushrooms immune system. But Thomas Richards, evolutionary biologist at the University of Oxford, UK, wonders whether a fungal immune system prevents the symbiosis - and whether mutations in this system could facilitate relationships. "I'm a big fan of this work," he adds.

Eva Nowack, microbiologist at the Heinrich Heine University Düsseldorf, Germany, was surprised at how quickly adjustments to the symbiotic life seemed to be created. In the future she would like to see what will happen after even longer periods; For example after more than 1,000 generations.

The development of such symbioses could lead to the creation of new organisms with useful properties, such as the ability to consume carbon dioxide or atmospheric nitrogen, says Vorholt. "This is the idea: to create new properties that an organism does not have and that would otherwise be difficult to implement."

1. Giger, G. H. et al. Nature https://doi.org/10.1038/s41586-024-08010-x (2024).

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2. Gäbelein, C. G., Reiter, M. A., Ernst, C., Giger, G. H. & Vorholt, J. A. ACS Synth. Biol. 11, 3388–3396 (2022).

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