JAN 09, 2018 7:00 AM PST

Unusual Gene Evolution in Bacteria

WRITTEN BY: Carmen Leitch

Researchers at the University of Montana researchers have discovered an extreme change in bacteria that lived within cicadas long ago. The alterations that took place at the cellular level can help us understand basic processes in biology shared among all life on Earth; these bacteria have lived inside of these insects since dinosaurs habited the planet. 

A Chilean cicada, which hosts particularly unusual symbiotic bacteria. / Credit: Piotr Lukasik

Over 70 million years, the bacteria had to lose an incredible 95 to 97 percent of their genes in order to live in the cicada. They now possess some of the smallest known genomes of any organisms, but they also can’t live anywhere else but inside of a cicada.

"Cicada symbiotic complexes are very different from any other known organism," noted Matt Campbell, a UM graduate candidate studying cicadas in the lab of UM biology Associate Professor John McCutcheon (part of the Division of Biological Sciences).

There are many examples of insects living in symbiotic relationships with hosts, in which both species need one another for critically important processes. In insects, that may mean the bacteria are helping the insects metabolize certain foods, and ensuring a supply of the right nutrients.

This work has indicated that the symbionts living in cicadas are synthesizing vital amino acids and vitamins that are needed by their insect hosts for growth and reproduction. Over three field seasons of studying a type of South American cicada, UM postdoctoral researcher Piotr Lukasik discovered that many of the bacteria living in symbiosis with the species evolved into complexes made of several different strains of bacteria in the same cicada.

"Through that process, individual bacteria have lost many genes and now depend on each other because every type contains unique, essential genes," Lukasik explained. "The different types must all work together to provide the amino acids and vitamins their cicada host requires."

A different kind of cicada that resides in the eastern United States hosts dozens of tiny bacteria that rapidly evolve. Individuals contain very few genes that are recognizable; they are also dispersed among different cell types in the cicada, which is not well understood.

"Cicadas host symbiotic complexes rather than a single, well-behaved bacteria, which could be a challenge for the species," Lukasik explained. "After all, when you need a meal - whether it is a vitamin required by a cicada or a pizza craved by a hungry student - it's easier to obtain it from a single source rather than cobbling it together from several different sources."

The investigators have suggested that this bacterial evolution has been a chance occurrence, and although it is not beneficial to the cicada, those microbes will now remain where they are. The cicada needs them for survival, now.

"Indeed, the cicadas with the longest life cycles are also those with the craziest bacterial symbionts," Lukasik said.


Some of McCutcheon’s previous work is outlined in the video above.

Sources: AAAS/Eurkealert! Via University of Montana, Current Biology, PNAS

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
MAR 17, 2020
Genetics & Genomics
MAR 17, 2020
Targeting RNA With CRISPR
Researchers screened thousands of target molecules to find the most effective targets, and have made their data openly a ...
APR 11, 2020
Cardiology
APR 11, 2020
Cell Transplant Repairs Brain After Stroke
Using cell therapy, researchers from Lund University in Sweden have successfully restored mobility and a sense of touch ...
APR 21, 2020
Cell & Molecular Biology
APR 21, 2020
Virtual Cell Provides a Close Look at Gene Expression During Development
Living organisms start out as one cell, and its genetic programs allow it to divide many times over, to give rise to the ...
MAY 22, 2020
Cell & Molecular Biology
MAY 22, 2020
Some Coral Turn Neon When Stressed
Corals are immobile animals, and coral reefs are considered to be the most diverse ecosystems in the sea.
MAY 26, 2020
Cell & Molecular Biology
MAY 26, 2020
The Lasting Glow of Tube Worm Slime
Tube worms are ancient creatures that can be found near hydrothermal vents on the seafloor. Their bioluminescence apears ...
JUN 01, 2020
Cell & Molecular Biology
JUN 01, 2020
Perchlorate in Drinking Water is More Dangerous Than Thought
Perchlorate dissolves easily and can be found contaminating drinking water in the United States.
Loading Comments...