A genômica microbiana desafia Darwin

sexta-feira, julho 08, 2016

Microbial genomics challenge Darwin

Source/Fonte: Nature Reviews Genetics

About this Research Topic

The 200th anniversary of Darwin’s birthday was celebrated in 2009, making the concept of Darwinism even more popular than at the time it was originally proposed, to the extent that it has acquired quasi-religious status. His theory revolves around a Tree of Life in which all living organisms are considered to have descended from a single ancestor, and each node represents a common ancestor. It comprises hierarchy and dichotomy, which are typical characteristics of the post-biblical 19th century vision. Indeed, according to post-modern philosophy (also called the French theory) the majority of theories, including scientific ones, are based only on meta-narratives expressing the influence of a culture at a given time. Buddhism or Hinduism may have generated a very different story of evolution. 

Our way of thinking about life, and the way we describe evolution, have changed radically in the 21st century due to the genomic revolution. Comparative genome analyses have demonstrated that gene repertoires are characterized by plasticity, and there is strong evidence that nearly all genes have been exchanged at some point. Genomic data show that the genetic information of living organisms is inherited not only vertically but also laterally. Lateral gene transfers were at first observed only in bacteria, which contain genes originating from eukaryotes, Archaea and viruses. Such transfers were subsequently identified in all living organisms; giant viruses have chimeric genomes and the human genome is a mosaic of genes with eukaryotic, bacterial, and viral origins. We cannot identify a single common ancestor for the gene repertoire of any organism. Furthermore, a very high proportion of genes have been newly created through gene fusion or degradation, and others show no homology to sequences found in other species. It is now clear that every living organism has a variety of ancestors, while exchanges between species are intense, and the creation of new genes is frequent and permanent in all living organisms. Our current genomic knowledge contradicts the tree of life theory, as established by Darwin. Recent analyses have produced bushes rather than resolved trees, with the structure of some parts remaining elusive. It becomes more and more obvious that phylogenetic relationships are better described by forests and networks and that species evolution looks more like a rhizome. The chimerism and mosaic structure of all living organisms through both non-vertical inheritance and de novo creation can only be assimilated and described by a post-Darwinist concept. 

In this Research Topic we wish to highlight the influence of microbiology and genomics on our understanding of the complexity of gene repertoires, and also demonstrate how current knowledge does not support Darwin’s theory. Microbiology has offered a great advance in the way we perceive life. Evidence obtained from studies on bacterial and viral evolution, lateral inheritance, phylogenetic trees and biodiversity continues to challenge what constituted, until recently, an unimpeded dogma in biology.