HOW SYMBIOSIS HELPS DEFINE EVOLUTION

by CJ SIEBENECK

AT THE U’S SCHOOL OF BIOLOGICAL SCIENCES, THE COLIN DALE LAB, ALONG WITH SARAH BUSH AND DALE CLAYTON HAVE JOINED WITH HUMAN GENETICIST ROBERT WEISS AND COLLABORATORS FROM THE UNIVERSITY OF ILLINOIS (KEVIN JOHNSON) AND VIRGINIA COMMONWEALTH UNIVERSITY (BRET BOYD) TO EXPLOIT AN AMAZING BIOLOGICAL SYSTEM.

Their focus: to study the relative contributions of stochasticity, contingency, and determinism towards evolution.

The target subject? Bird lice! Their diets consist almost solely of feather keratin, which is deficient in B-vitamins. It’s a deficiency that symbiotic bacteria can rectify, and every bird louse has independently used this solution by “domesticating” them as B-vitamin factories. This symbiotic relationship creates an evolutionary safety net where the bacteria can afford to lose genes whose functions are complemented by their host. In a field dominated by stochastically (randomly) generated mutations, a deeper understanding begins to emerge.

“The resulting approaches are really novel and uncover striking and highly supported patterns,” says Colin Dale, principal investigator and co-author of a paper published last summer in Nature Communications: “Stochasticity, determinism, and contingency shape genome evolution of endosymbiotic bacteria.” “Such approaches also have great potential for understanding the etiologies of diseases such as cancer, that often arise as a consequence of gene(s) becoming damaged.”

The findings of this research are possible thanks to a dream-team mitochondria or chloroplasts in plants. These have been theorized to have once been independent microbes, showing that when a larger organism can consistently supply nutrients, evolution allows the symbiont to further benefit its host. Traits like photosynthesis originated through such a process, which we can now better define. collaboration between global field workers and, in Dale’s words, “The silicon bubble of computational biology.” Bush and Clayton, along with many other collaborators, have been collecting and studying bird lice for decades, yielding a gift to science that keeps on giving. They then pass the fruits (or lice) of their labor to graduate students like Ian James, who craft complex data analysis pipelines to obtain insight from those sets of data.

It's a growing system that has been used to answer important questions in the field of evolutionary biology, presenting implications for the evolution of structures like mitochondria or chloroplasts in plants. These have been theorized to have once been independent microbes, showing that when a larger organism can consistently supply nutrients, evolution allows the symbiont to further benefit its host. Traits like photosynthesis originated through such a process, which we can now better define.

“In the context of symbiosis, this system is actually really interesting because it’s so boring,” quips Dale. “The lack of variation in the underlying biology makes it an excellent candidate for this type of study. I’ve always paid attention to the aphorism stating that ‘all that glitters is not gold.’ It’s also worth noting that sometimes the gold doesn’t glitter at all.”

A longer version of this story can be found at biology.utah.edu/news.