Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Final Activity and Management Report Summary - GENOME EVOLUTION (Tracing the evolution of alpha-proteaobacterial genomes)

Although invisible to the naked eye, bacteria have played important roles, not only for us, humans, but also at a larger scale: They drive fundamental biochemical processes that are crucial for sustaining life on planet Earth. One way to obtain fundamental insight in how bacteria drive these processes, is to study their genetic. During the past decennia, methods have been developed that allow for the elucidation of complete genomes of organisms, revealing all the genes encoded within it.

The current study aims at gaining insight in a specific class of bacteria designated the alpha-proteobacteria, for the following reasons:
(i) Alpha-proteobacteria are among the most ubiquitous and versatile bacteria currently known to man and, as such, they represent an evolutionary extremely successful group. In addition
(ii), alpha-proteobacteria have been shown to interact with highly developed life, including us, humans. Some alpha-proteobacterial species are known causative agents of diseases and epidemics.
Finally (iii), alpha-proteobacteria are interesting from an evolutionary point of view, as mitochondria, essential energy-generating organelles of eukaryotic cells, have emerged from an ancestral-type of alpha-proteobacterium.

By studying the alpha-proteobacterial genomes, the current study has tried to gain insight in the genome evolution of alpha-proteobacteria, thereby revealing several interesting features. For example, the genome sequences of the alpha-proteobacterial SAR11 group, which are perhaps to most abundant life forms on the planet, were found to be exceptionally small, having been subjected to extreme genome reduction. Intriguingly, the SAR11 genomes were missing a number of genes involved in the maintenance of their genetic integrity. We argue that the absence of these genes, which were present in all other known alpha-proteobacterial species, might underlie their success in terms of overall abundance of this group of bacteria on the planet.

In addition, our study focused on the identification of alpha-proteobacterial species that represented distant relatives to the ancestor of the mitochondria. In a so-called metagenomics approach, in which large amounts of environmental sequence data from the ocean surface waters was analysed, we managed to identify gene fragments that indeed might indeed belong to an alpha-proteobacterial species with a distant relationship to mitochondria.

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