Evolution: microbiome of coral (Evolution)

by David Turell , Saturday, November 24, 2018, 19:20 (2189 days ago) @ David Turell

Bacteria and other organisms are everywhere and obviously play a role in evolution as microbiomes:

https://phys.org/news/2018-11-corals-microbiomes-evolved.html

"Corals and the microbes they host evolved together, new research by Oregon State University shows.

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"Modern corals are home to a complex composition of dinoflagellates, fungi, bacteria and archaea that together make up the coral microbiome. Shifts in microbiome composition are connected to changes in coral health.

"'Likely the ancestral corals also harbored complex microbial communities but there's a lot we don't know about how these coral-microbe symbioses evolved or the key factors influencing microbial communities in modern corals," Vega Thurber said. "Certain species of corals have distinct microbiomes, to the point where that occurred at some point in their evolutionary history. Not 400 million years ago, but there are specific groups of microbes that do show very strong evidence of evolving with their hosts more recently."

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"On a lot of different scales, the more similar the coral hosts, the more similar the microbial communities are—both the whole community and particular microbes," McMinds said. "We collected samples from as many kinds of corals as was possible. For every sample set, we looked at the corals' tissue, skeleton and mucus to see what microbes were there."

"To do that, the researchers sequenced the 16S rRNA gene. The gene is present in every living organism, McMinds explains, but is slightly different. He likened it to a "molecular bar code" of each organism it belongs to.

"From there, the scientists could look for patterns between different corals' microbial communities and determine whether co-evolution of the corals and their microbiomes had taken place.

"'We found strong support for coral-microbe 'phylosymbiosis,' in which coral microbiome composition and richness is reflected in coral host's evolutionary history," Vega Thurber said. "When speciation for modern reef-building coral families began between roughly 25 million and 65 years ago, that was accompanied by large changes in microbiome richness. And changes continued to accumulate during more recent speciation events."

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"It was something of a surprise to researchers to find that the microbial communities of the corals' calcium carbonate skeletons showed greater microbiome richness compared to the tissue and mucus microbiomes. Also, the skeletal microbiomes displayed the strongest signal of long-term phylosymbiosis—a pattern in which the diversification of a related group of host organisms correlates with changes in dissimilarities among their microbiomes.

"'We originally thought corals would show signs of phylosymbiosis throughout their entire phylogenetic history, and the results support that for the skeleton and tissue but not the mucus," McMinds said. "Despite variability in the chemical composition of mucus between species and significant host-specificity in the mucus microbiome, host specificity was limited to relatively recent divergences.'"

Comment: This line of research is just beginning, but there is no question that life
may have started with bacteria, but they have remained active to influence evolution over time in the multicellular forms that followed them..