A simple bacteria reveals how stress drives evolution – Phys.Org

July 20, 2017 by Elizabeth Howell , Astrobiology Magazine The researchers examined the biological processes of E.coli, a common bacteria. Credit: NIAID

A common bacteria is furthering evidence that evolution is not entirely a blind process, subject to random changes in the genes, but that environmental stressors can also play a role.

A NASA-funded team is the first group to design a method demonstrating how transposonsDNA sequences that move positions within a genomejump from place to place.

The researchers saw that the jumping rate of these transposons, aptly-named "jumping genes," increases or decreases depending on factors in the environment, such as food supply.

"This is a new window into how environment can affect evolution rates," said Nigel Goldenfeld, director of the NASA Astrobiology Institute for Universal Biology at the University of Illinois at Urbana-Champaign. "We can measure evolution rates for the first time, and we can see evolution acting at the molecular level."

Thomas Kuhlman, a physicist at the University of Illinois, Urbana-Champaign, said bacteria species can also play a role in jumping rates, as well as the environment.

"The activity of these transposal elements is not uniformly random; it's not just a pile of cells," he said.

Kuhlman and Goldenfeld recently published a paper on the research, "Real-time transposable element activity in individual live cells," in the Proceedings of the National Academy of Sciences. The research was led by Neil Kim, a physics graduate student at the University of Illinois at Urbana-Champaign, and also included work from fellow students Gloria Lee, Nicholas Sherer and Michael Martini.

True colors

Goldenfeld studies the role of the environment on evolution, while Kuhlman focuses on the biological processes of E. coli, a common bacteria that lives in the digestive tracts of humans and animals and the cause of infections by way of contaminated feces.

The two researchers came up with a novel approach to watching the movement of jumping genes by engineering an E. coli that expresses a fluorescent protein when the transposons "jump" out of a genome. Because the cell lights up when this occurs, the researchers were able to record the cells that jump more than others.

"The cells light up only when a transposon jumps," Goldenfeld said. "So we can see how often they jump, and when they jump, and where they jump from."

Goldenfeld's team also constructed a computer simulation of the jumping activity that was able to rule out random activity as the primary reason for jumping. Once they compared the simulation with the laboratory trials, it was clear that the transposons were not jumping randomly. Goldenfeld said the findings shed more light on the mechanisms of evolution.

A fundamental assumption of evolution has been that mutations and other instabilities in the genomes randomly occur in an organism as a 'blind" evolutionary force, and those that are beneficial to the cell lead to reproductive success. Another possibility, less accepted by biologists, is that the environment prompts the cell or organism to mutate in order for the cell to prosper better. These adaptive mutations, or stress-induced mutations, occur in response to stressors in the environment.

"Our work shows that the environment does affect the rate at which transposons become active, and subsequently jump into the genome and modify it," Goldenfeld said. "Thus the implication is that the environment does change the evolution rate. What our work does not answer at this point is whether the transposon activity suppresses genes that are bad in the particular environment of the cell. It just says that the rate of evolution goes up in response to environmental stress.

"This conclusion," he added, "was already known through other studies, for certain types of mutation, so is not in itself a complete reversal of the current dogma. We hope that future work will try to measure whether or not the genome instabilities that we can measure are adaptive."

Kuhlman said he has hopes of future research on more complex organisms.

"The next step is operating in yeast, as a very simple eukaryotic cell. Then eventually much further down the road, we'll get [the process] working in mammalian or human cells."

The research is not only useful for understanding the origins of life, but also uncovering situations where cells undergo rapid mutations. One possible application could be routing out the pathways of cancer, which happens when cells abnormally grow and cause problems with the rest of the body.

Goldenfeld added that the findings also have clear implications to astrobiology.

"One of the things that astrobiology is concerned with is the interaction between the environment and the rate of evolution," he said. "Our work showed for the first time that there are environmental influences on the rate of transposon activity, because we could literally measure the effect. We did this quantitatively and compared it with theoretical predictions that assumed that transposon activity was random. We could show that the activity is not random at all."

The NASA Astrobiology Institute funded the research.

Explore further: Watching 'jumping genes' in action

More information: Neil H. Kim et al. Real-time transposable element activity in individual live cells, Proceedings of the National Academy of Sciences (2016). DOI: 10.1073/pnas.1601833113

This story is republished courtesy of NASA's Astrobiology Magazine. Explore the Earth and beyond at http://www.astrobio.net .

"Jumping genes" are ubiquitous. Every domain of life hosts these sequences of DNA that can "jump" from one position to another along a chromosome; in fact, nearly half the human genome is made up of jumping genes. Depending ...

Nature is full of parasitesorganisms that flourish and proliferate at the expense of another species. Surprisingly, these same competing roles of parasite and host can be found in the microscopic molecular world of the ...

By inserting an amyotrophic lateral sclerosis (ALS)-linked human gene called TDP-43 into fruit flies, researchers at Stony Brook University and Cold Spring Harbor Laboratory discovered a potential role for 'transposons' in ...

The vesper bats are the largest and best-known common family of bats, with more than 400 species spread across the globe, ranking second among mammals in species diversity.

The genome is not a fixed code but flexible. It allows changes in the genes. Transposons, however, so-called jumping genes, interpret this flexibility in a much freer way than "normal" genes. They reproduce in the genome ...

The human genome shares several peculiarities with the DNA of just about every other plant and animal. Our genetic blueprint contains numerous entities known as transposons, or "jumping genes," which have the ability to move ...

Cutting through the ocean like a jet through the sky, giant bluefin tuna are built for performance, endurance and speed. Just as the fastest planes have carefully positioned wings and tail flaps to ensure precision maneuverability ...

Researchers at the University of California, Berkeley, have discovered how Cas1-Cas2, the proteins responsible for the ability of the CRISPR immune system in bacteria to adapt to new viral infections, identify the site in ...

Instead of having more children, a grandmother may pass on her genes more successfully by using her cognitive abilities to directly or indirectly aid her existing children and grandchildren. Such an advantage could have driven ...

A study in fruit flies suggests that existing approaches to gene drives using CRISPR/Cas9, which aim to spread new genes within a natural population, will be derailed by the development of mutations that give resistance to ...

Every day, humans pick up on idiosyncrasies such as slow drawls, high-pitched squeaks, or hints of accents to put names to voices from afar. This ability may not be as unique as once thought, researchers report on July 20 ...

University of South Florida biologists have found that a crucial window in the development of tadpoles may influence a frog's later ability to fight infectious diseases as an adult.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more