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:2/1/2016)... 2016  Today, the first day of American Heart ... develop a first of its kind workplace health solution ... In the first application of Watson ... ), and Welltok will create a new offering that ... analytics, delivered on Welltok,s health optimization platform. The effort ...
(Date:1/27/2016)... CHESTER, Ohio , Jan. 27, 2016  Rite ... supplier based in West Chester, Ohio ... their award winning service staff, based in ... technical capacity and ability to provide modifications, installations and ... John Dovalina , CEO of PLUS, commented, "PLUS has ...
(Date:1/22/2016)... , January 22, 2016 ... the addition of the  "Global Behavioral ... offering. --> http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) ... "Global Behavioral Biometric Market 2016-2020"  report ... Research and Markets ( http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) has ...
Breaking Biology News(10 mins):
(Date:2/11/2016)... 11, 2016  Dovetail Genomics™ LLC today announced that ... for a planned metagenomic genome assembly service. Richard ... genome assembly method in a talk on Friday, February ... Technology conference in Orlando, Fla. ... datasets is difficult. Using its proprietary Chicago ...
(Date:2/11/2016)... ... , ... Global Stem Cells Group, has announced ... new facility will provide advanced protocols and state-of-the-art techniques in cellular medicine, focusing ... The new GSCG clinic is headed by four prominent Ecuadorian physicians, including Pablo ...
(Date:2/10/2016)... , Feb.10, 2016 ASAE is introducing a ... Management Companies (AMC) the option of joining or renewing ... fee determined by staff size, every employee in any ... ASAE and reap all available member benefits.   ... new organizational membership options will allow organizations of any ...
(Date:2/10/2016)... ... February 10, 2016 , ... Benchmark ... today the promotion of two long-standing principal investigators (PI) to the roles of ... Research and Development. , Dr. Laurence Chu, a Benchmark Research PI in the ...
Breaking Biology Technology: