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Research points to land as origin for Earth's microbes


December 24, 2008

Fabia Battistuzzi, a new Biodesign postdoc in the lab of Dr. Sudhir Kumar, recently made an important contribution to our understanding of the evolution of life on Earth that has the prestigious journal Nature taking notice. Her research, performed in the lab of long-time Kumar collaborator Blair Hedges of Pennsylvania State University, argues that nearly two-thirds of all bacteria species “share a common ancestor that was adapted to life on land,” according to the Nature news spotlight article.

“It seems that all of these groups had a terrestrial common ancestor three billion years ago,” said Hedges.

For their experimental approach, the team compared sequences of RNA, the chemical messenger molecule that carries out DNA instructions in the cell to create a molecular tree of life, called phylogenetic analysis. Those sequences that have more in common are more closely related on the tree compared to more distant species, whose sequences diverge.

Battistuzzi came upon the team’s discovery when comparing the differences between bacterial species in the core chemical units of RNA, known for their one letter abbreviations of A, C, T, or G. “When we looked at the ribosomal RNA tree we noticed a bias in the deepest branches that was caused by a higher content of guanines [G] and cytosines© compared to adenines [A] and thymines [T] in those lineages. When we compensated for this bias the phylogeny changed to resemble the one obtained by an independent protein data set. This is the first time the two data sets are in agreement not only with each other, but also with cellular characteristics and the environmental distribution of prokaryotes.”

The research has already generated an intense debate among the scientific research community as chronicled in the Nature article.

During her postdoctoral research within the institute’s Center for Evolutionary Functional Genomics, directed by Dr. Kumar, Battistuzzi hopes to deepen our understanding of life’s evolutionary history, from ancient to recent speciation events, and also uncover genomic evolutionary mechanisms. “To achieve this, it is important to ameliorate current computational methods and develop new strategies to analyze an increasing amount of genomic information.”