New Lightweight Champion of Genomes

Chris Venter, a genome sequencing pioneer of San Diego, California, and his team have released a report describing their recently engineered bacteria with the smallest genome of any freely living organism ever recorded.

This synthetic organism has been strapped down to only the bare minimum of potentially the only genes necessary to survive and reproduce. Unlike the genome of 20,000-25,000 possessed by humans, or the heavyweight champion Japanese flower that is comprised of 50 times more DNA than humans, this new bacteria known as Syn. 3.0 is comprised of only an astounding 473 genes.Venter's previous work had created the Syn 1.0, which had a genome of 901. In an attempt to shrink the genome smaller than the leading minimal genome of 525 in Mycoplasma genitalium, Vetner's large team of colleagues broke up into teams for each section of the bacteria's genome and kept stripping genes from Syn 1.0 with functions that were either nonessential or duplicated the function of another gene until they had a viable organism with a smaller genome than the previous leader.   

Venter claims him and his team designed and tested "multiple hundreds" of constructs until they settled on Syn 3.0. Compared to M. genitalium which can take weeks for a population of its cells to double, Syn 3.0's slimmed down genome is able to double in 3 hours. The function of 149 of Syn 3.0's 473 genes still remain unknown, which leads way to further investigations and insights into the basic biology of life. Evolutionary biologists and biotechnologists are claiming to also start adding genes back to the genome of 3.0 to study their effects. 

This is extremely exciting stuff, as it basically tells us that biologists have been paved a path for new discoveries. Syn 3.0 seems like the key to a new doorway of genetics which could potentially help lead to discoveries that just might end up in the school textbooks of the future. 

  

Tiny bird, tiny genome

Scientists have determined that hummingbirds have the least amount of DNA compared to all other birds, reptiles, or mammals.   This reduced DNA is evident in all species of hummingbirds, indicating that the DNA was pared down before speciation.  Scientists have also identified a link between small amounts of DNA and higher metabolic rates.  It is believed that smaller genomes allow for smaller cells and a resulting larger surface-to-volume cell ratio.  This link is evident not only in hummingbirds, but also in most other birds and bats.



This study is being conducted by Ryan Gregory and his colleagues at the University of Guelph in Canada.  By staining DNA in the nucleus and analyzing it’s density, they have estimated the genome size of 37 species of hummingbirds.   Scientists believe hummingbirds may have the smallest genomes and the highest metabolic rates theoretically possible.

I found this article very interesting.  Hummingbirds are one of my favorite animals and I was intrigued by the genetic links between their genome lengths and metabolic rates.  The proposed relationship between surface-to-volume cell ratio and metabolic rate makes perfect sense and I am curious as to what other organisms also display this relationship.