New findings show how bacteria undergo genome evolution

Scientists at the Institut Pasteur and the University of Maryland have revealed how bacterial and archaea microbes successfully evolve their gene repertoires to face new challenges, predominantly by acquiring genes from other individuals. The study, published in the open-access journal PLoS Genetics on January 27, was instigated to clarify the role of gene duplication, an important source of novelty in multicellular organisms, in bacteria.

Microbes live and thrive in incredibly diverse and harsh conditions, from boiling or freezing water to the human immune system. This remarkable adaptability results from their ability to quickly modify their repertoire of protein functions by gaining, losing and modifying their genes. Microbes were known to modify genes to expand their repertoire of protein families in two ways: via duplication processes followed by slow functional specialization, in the same way as large multicellular organisms like us, and by acquiring different genes directly from other microbes. The latter process, known as horizontal gene transfer (HGT), is notoriously conspicuous in the spread of antibiotic resistance, turning some bacteria into drug-resistant 'superbugs' such as MRSA (methocillin-resistant Staphylococcus aureus), a serious public health concern.

The researchers examined a large database of microbial genomes, including some of the most virulent human pathogens, to discover whether duplication or HGT was the most common expansion method. They show that gene family expansion can indeed follow both routes, but unlike large multicellular organisms, it predominantly takes place by horizontal transfer. Thus, quick diversification of microbial functions results from the recruitment by microbes of pre-existing adaptations from other microbes.

The study concludes with the observation that, since microbes invented the majority of life's biochemical diversity, from respiration to photosynthesis, we must recognize the predominant role of HGT in the diversification of all protein families.

FINANCIAL DISCLOSURE: This study was carried out with financial assistance from the Institut Pasteur and the Centre National de la Recherche Scientifique. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

COMPETING INTERESTS: The authors have declared that no competing interests exist.

CITATION: Treangen TJ, Rocha EPC (2011) Horizontal Transfer, Not Duplication, Drives the Expansion of Protein Families in Prokaryotes. PLoS Genet 7(1): e1001284. doi:10.1371/journal.pgen.1001284

PLEASE ADD THIS LINK TO THE FREELY AVAILABLE ARTICLE IN ONLINE VERSIONS OF YOUR REPORT (the link will go live when the embargo ends): http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1001284

PRESS-ONLY PREVIEW OF THE ARTICLE: http://www.plos.org/press/plge-07-01-treangen.pdf

CONTACT:
Todd Treangen
treangen@pasteur.fr

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