Strange microbial partnership shows how complex life may have evolved

Microbes from a remote bay in western Australia appear to connect to each other with small pipes, which forms a relationship that can reflect an early step in the development of complex life.

In Shark Bay or Gathaagudu in the original MGANA language, microbes form slimy multilayer communities called microbial mats. It is a hard environment bound by tides and temperature fluctuations, but these communities of bacteria and another kind of single cell organ called Archaea have survived here for tens of thousands of years. They often live in symbiosis with each other and build their community into layered sedimentary called stromatolites.

“The mats are formed under hyper-salt conditions with high UV levels. They are affected by cyclones. Almost everything seems to be smashing these things, but they still seem to hang around,” Brendan Burns said at the University of New South Wales in Sydney.

They are modern analogs of how communities with microbes can have the nest that lives together billions of years ago when complex life first evolved, he says. This is theorized to have happened as bacteria and Archaea became so mutual depends on another that the bacteria and Archaea, creating more complex cells known as eukaryotes.

Burns and his colleagues have some of these microbial mat communities back to their laboratory and tried to grow the organs under high salt, low oxygen conditions.

They ended up with a culture with only one bacteriart, Stromatodesulfibrio nilemahensisand a recently named archaeon, Nerearchaeum marumarumayaeFrom a group called Asgard Archaea. These Archaea are named after the gods’ home in Norrøn mythology and is believed to be the closest living relatives of eukaryotic cells that make up our bodies and other animals and plants.

“These organizations seem to interact directly with each other and exchange nutrients,” says team member Iain Duggin at the University of Technology Sydney. The team does not have direct evidence of it, but they have complete genome sequences that allow them to derive how metabolism from both organizations works.

The sequencing showed that the bacterium produces acids and vitamins, and the archaeon produces hydrogen and compounds such as acetate, format and sulfite. Both sets of products are not made from the other species, but would be downed by them.

The researchers also saw the hints that the two species directly interacted. “What we did is observing is what we call nanor tubes,” says Dugine. “Small tubes that appear to be made of the bacterium and connect directly to the outside of the Asgard cell.”

In what may have been part of the collaboration, the archaeon cells produced chains of vesicles, SAC-like structures used by cells to transport molecules, fastened with extracellular fibers. Duggin says the small vesicles from the archaeon seem to interact with the nanor tubes generated by the bacterium.

“The nanotubulies may also be wiring, but they can help tie the cells together in an excursion of multicellular union that allows them to bet share resources,” says Duggin.

The researchers also found genome sequences the code for proteins that never have before, and a protein that is about 5500 amino acids long, which is very large for an Archaeal species that bears similarities to proteins in human muscles. “I’m not doing it, it’s a human muscle protein, but it suggests that the development of these proteins could have started a very long time ago,” says team member Kate Michie at the University of New South Wales.

“What I find most interesting are these direct relations from nanor tubes between the bacteria and Archaea,” says Puri López-García at the University of Paris-Saclay in France. “This has not been observed in past cultures.”

However, it is difficult to know what the bacteria and Archaea are recently doing, says Buzz Baum at the MRC Laboratory of Molecular Biology in Cambridge, UK. “Bacteria and Archaea are at war and peace with each other,” he says. “They touch each other, share, fight and who knows what’s going on.”

Duggin believes that in this case it is more likely to be peace than war. “Becuse these organizations have out of Eded together in our cultures after four or more years, we think they mind each other’s company and probably come on loans,” he says.

Burns and his colleagues offer that what they have seen may reflect an early step in the development of eukaryotic cells on microbial mats, as Roland Hatzenpichler at Montana State University says may be possible.

“The results of the study show that the recently found Asgard Archaea directly interacts with sulfate-reducing bacteria, which could give a driving force to a much closer-and ultimately possible mandatory mandatory [dependent] – Interaction, ”he says.

This may not be what happened more than 2 billion years ago, says López-García. “These are modern Archaea and modern bacteria, although the microbial mud they live in may consider analogues of some previous ecosystems.

We may never know the extent to which modern microbes are similar to the cells that parted to form the proto-eukaryotic cell, says Hatzenpichler. “But we are now in a better position than ever to approach the truth.”

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