Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài: Accelerated evolution associated with genome reduction in a free-living prokaryote. | Research Open Access Accelerated evolution associated with genome reduction in a free-living prokaryote Alexis Dufresne Laurence Garczarek and Frédéric Partensky Address Station Biologique UMR 7127 CNRS et Université Paris 6 BP74 29682 Roscoff Cedex France. Correspondence Frédéric Partensky. E-mail partensky@ Published 14 January 2005 Genome Biology 2005 6 R14 The electronic version of this article is the complete one and can be found online at http 2005 6 2 R14 Received 5 October 2004 Revised 2 December 2004 Accepted 7 December 2004 2005 Dufresne et al. licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License http licenses by which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Abstract Background Three complete genomes of Prochlorococcus species the smallest and most abundant photosynthetic organism in the ocean have recently been published. Comparative genome analyses reveal that genome shrinkage has occurred within this genus associated with a sharp reduction in G C content. As all examples of genome reduction characterized so far have been restricted to endosymbionts or pathogens with a host-dependent lifestyle the observed genome reduction in Prochlorococcus is the first documented example of such a process in a free-living organism. Results Our results clearly indicate that genome reduction has been accompanied by an increased rate of protein evolution in P. marinus SS120 that is even more pronounced in P. marinus MED4. This acceleration has affected every functional category of protein-coding genes. In contrast the 16S rRNA gene seems to have evolved clock-like in this genus. We observed that MED4 and SS120 have lost several DNA-repair genes the absence of which could be related to the mutational bias and the acceleration of amino-acid substitution. Conclusions .
