Navigation Links
Ready, set, mutate?and may the best microbe win

Even with modern genomic tools, it's a daunting task to find a smoking gun for Darwinian evolution. The problem lies in being able to say not just when and how a specific gene mutated but also how that one genetic change translated into real-world dominance of one population over another.

Rice University biologists, using an ingenious experiment that forced bacteria to compete in a head-to-head contest for evolutionary dominance, today offer the first glimpse of how individual genetic-level adaptations play out as Darwinian natural selection in large populations. The results appear in the May 19 issue of Molecular Cell.

"One of our most surprising findings is that an estimated 20 million point mutations gave rise to just six populations that were capable of vying for dominance," said lead researcher Yousif Shamoo, associate professor of biochemistry and cell biology. "This suggests that very few molecular pathways are available for a specific molecular response, and it points to the intriguing possibility of developing a system to predict the specific mutations that pathogens will use in order to become resistant to antibiotics."

Rice's study involved the heat-loving bacteria G. stearothermophilus, which thrives at up to 73 degrees Celsius (163 F). Shamoo and graduate students Rafael Couñago and undergraduate Stephen Chen used a mutant strain of the microbe that was unable to make a key protein that the bacteria needed to regulate its metabolism at high temperatures. They grew the bacteria for one month in fermentor, raising the temperature a half degree Celsius each day.

Over a span of 1,500 generations, the percentage of mutant strains inside the fermentor ebbed and flowed as the single-celled microbes competed for dominance. Eventually, one strain squeezed out almost all the competition by virtue of its ability to most efficiently metabolize food at high temperature.

The metabolic protein required to thrive at high-temperatu re could only be made in one genetic region of the bacteria's DNA, meaning the researchers had only to characterize that small region of the genome for each new strain in order to measure evolutionary progress.

The researchers sampled the fermentor for new strains every other day. Though millions of mutations in the target gene are believed to have occurred, only about 700 of those were capable of creating a new variant of the target gene. In all, the researchers identified 343 unique strains, each of which contained one of just six variants of the critical gene.

The first of the six, dubbed Q199R, arose almost immediately, and was the dominant strain through the 500th generation. Around 62 degrees Celsius, the Q199R was unable to further cope with the rising temperature, and a new round of mutations occurred. Five new varieties ?themselves mutant forms of Q199R ?vied for final domination of the fermentor. Three of the five were driven to extinction within a couple of days, and the final two fought it out over the remaining three weeks of the test.

The research included a raft of additional experiments as well. The team characterized each of the mutant proteins to document precisely how it aided in metabolic regulation. The fermentor experiment was repeated and the same mutations ?and no others ?were observed to develop again. Three of the six genes ?the "winner," it's closest competitor and Q199R ?were spliced back into the original form of the bacteria and studied, to rule out the possibility that mutations in other genes were responsible for the competitive advantage.

Shamoo said it's significant that the mutations didn't arise where expected within the gene. Four of the six occurred in regions of the gene that are identical in both heat-resistant and non-heat-resistant forms of G. stearothermophilus. Shamoo said this strongly shows the dynamic nature of evolution at the molecular and atomic level.

Shamoo said the most prom ising finding is the fact that the follow-up test produced precisely the same mutant genes.

"The duplicate study suggests that the pathways of molecular adaptation are reproducible and not highly variable under identical conditions," Shamoo said.


'"/>

Source:Rice University


Related biology news :

1. W.M. Keck Foundation funds study of friendly microbes
2. Yellowstone microbes fueled by hydrogen, according to U. of Colorado study
3. Scientists discover unique microbe in Californias largest lake
4. Harnessing microbes, one by one, to build a better nanoworld
5. Leprosy microbes lead scientists to immune discovery
6. Could microbes solve Russias chemical weapons conundrum?
7. Genome study of beneficial microbe may help boost plant health
8. Proteomics brings researchers closer to understanding microbes that produce acid mine drainage
9. Deep thinking: Scientists sequence a cold-loving marine microbe
10. Freeze-dried mats of microbes awaken in Antarctic streambed
11. MBL researchers probe how an ancient microbe thrives and evolves without sex
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:1/11/2017)... 11, 2017 Intoxalock, a leading ignition interlock ... of its patent-pending calibration device. With this new technology, ... securely upload data logs and process repairs at service ... "Fighting drunk driving through the application of cutting-edge ... large, but also for the customer who can get ...
(Date:1/6/2017)...  Delta ID Inc., a leader in consumer-grade iris ... at CES® 2017. Delta ID has collaborated with Gentex ... use of iris scanning as a secure, reliable and ... a car, and as a way to elevate the ... Delta ID and Gentex will demonstrate (booth #7326 LVCC) ...
(Date:12/22/2016)... , Dec. 20, 2016  As part of its longstanding ... leading personal genetics company, recently released its latest children,s book, ... The book focuses on the topics of inheritance and variation ... Standards (NGSS) taught in elementary school classrooms in the US. ... series by illustrator Ariana Killoran , whose previous book ...
Breaking Biology News(10 mins):
(Date:1/23/2017)... ... 2017 , ... AxioMed will be presenting its viscoelastic cervical ... Montego Bay, Jamaica from January 26-28th. “We’re excited to be presenting the benefits ... the simplicity of the surgical technique,” said Jake Lubinski, President of AxioMed. ...
(Date:1/21/2017)... ... 20, 2017 , ... G&L Scientific Inc, a leading provider ... ), has announced the opening of new offices in Cambridge, Massachusetts, strengthening and ... This is the latest step in G&L’s expansion of its global clinical consulting ...
(Date:1/21/2017)... CA (PRWEB) , ... January 21, 2017 , ... ... our ongoing endeavors to bring to market a pioneering medical device for the ... has signed an engagement contract with Emergo, a global regulatory consultancy that helps ...
(Date:1/21/2017)... BOULDER, Colo. , Jan. 20, 2017 ... ("Bioptix" or the "Company"), announced that on January 14, ... a plan under which the Company will terminate certain ... subsidiary, Bioptix Diagnostics, Inc.  The Company commenced terminations on ... completed within 30 days.  The Company may pay severance ...
Breaking Biology Technology: