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Sunday, October 22nd 2006

Watching Symbiosis In Work

Watching as a symbiotic bacterium evolves into an organelle.


Is A New Organelle Slowly Evolving In this Guy?

University of Arizona biologist Nancy Moran, a coauthor of the Carsonella [rudii] study, said that when she and her colleagues first sequenced the genome, it was so small that they assumed their measuring procedure wasn’t working properly. But when they outsourced the sequencing work to a lab in Japan, those scientists got the exact same results.

Moran said that Carsonella has genes missing for nearly every essential cell process, including those that are involved in DNA replication, the transcription of DNA to RNA, and the translation of RNA inHto proteins. The most obvious hypothesis for how the bacterium continues to survive, she said, is that some of its genes may have transferred from the symbiont’s genome to the host insect’s genome. The host, an insect called the psyllid, may now be expressing those bacterial genes and sending their protein products back into the Carsonella cells.

“That hypothesis could explain how this organism is still able to replicate and to persist,” Moran said. “And the reason that hypothesis suggests itself is that is what happens in the case of the cell organelles, like mitochondria and plastids.”

If this is indeed what has happened, according to Moran, Carsonella will never be independent again, and it may be rapidly evolving into an organelle of the psyllid. She added that the bacterium has retained its ability to make nutritional amino acids for the psyllid, so the relationship is truly symbiotic.

H/T Reddit

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