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- Andersson, Siv G E, et al.
(författare)
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Comparative genomics of microbial pathogens and symbionts.
- 2002
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Ingår i: Bioinformatics. - 1367-4803 .- 1367-4811. ; 18 Suppl 2, s. S17-
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Tidskriftsartikel (refereegranskat)abstract
- We are interested in quantifying the contribution of gene acquisition, loss, expansion and rearrangements to the evolution of microbial genomes. Here, we discuss factors influencing microbial genome divergence based on pair-wise genome comparisons of closely related strains and species with different lifestyles. A particular focus is on intracellular pathogens and symbionts of the genera Rickettsia, Bartonella and BUCHNERA: Extensive gene loss and restricted access to phage and plasmid pools may provide an explanation for why single host pathogens are normally less successful than multihost pathogens. We note that species-specific genes tend to be shorter than orthologous genes, suggesting that a fraction of these may represent fossil-orfs, as also supported by multiple sequence alignments among species. The results of our genome comparisons are placed in the context of phylogenomic analyses of alpha and gamma proteobacteria. We highlight artefacts caused by different rates and patterns of mutations, suggesting that atypical phylogenetic placements can not a priori be taken as evidence for horizontal gene transfer events. The flexibility in genome structure among free-living microbes contrasts with the extreme stability observed for the small genomes of aphid endosymbionts, in which no rearrangements or inflow of genetic material have occurred during the past 50 millions years (1). Taken together, the results suggest that genomic stability correlate with the content of repeated sequences and mobile genetic elements, and thereby indirectly with bacterial lifestyles.
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| 2. |
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| 3. |
- Klasson, Lisa, et al.
(författare)
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Evolution of minimal-gene-sets in host-dependent bacteria
- 2004
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Ingår i: Trends in Microbiology. - : Elsevier BV. - 0966-842X .- 1878-4380. ; 12:1, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- Several attempts have been made to identify the minimal set of genes that is required for life using computational approaches or studies of deletion mutants. These experiments resemble those already performed by nature; a few hundred million years ago an ancestor of Escherichia coli was domesticated by aphids, which resulted in the elimination of 70–75% of the original bacterial genome. Amazingly, the small genomes of these imprisoned bacteria are more stable than those of their free-living relatives. Minimal-gene-sets that have evolved naturally are largely species-specific, with the exception of a small set of core genes that are required for information processing. Comparative genomics of host-dependent bacteria have shown that minimal-gene-sets can persist in nature for tens of millions of years provided that the environment is rich in nutrients, that the host population size is large and that there is a strong host-level selection for bacterial gene functions.
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| 4. |
- Mira, Alex, et al.
(författare)
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Microbial genome evolution : sources of variability.
- 2002
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Ingår i: Current Opinion in Microbiology. - 1369-5274 .- 1879-0364. ; 5:5, s. 506-12
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Tidskriftsartikel (refereegranskat)abstract
- Comparative genome analyses of close relatives have yielded exciting insight into the sources of microbial genome variability with respect to gene content, gene order and evolution of genes with unknown functions. The genomes of free-living bacteria often carry phages and repetitive sequences that mediate genomic rearrangements in contrast to the small genomes of obligate host-associated bacteria. This suggests that genomic stability correlates with the genomic content of repeated sequences and movable genetic elements, and thereby with bacterial lifestyle. Genes with unknown functions present in a single species tend to be shorter than conserved, functional genes, indicating that the fraction of unique genes in microbial genomes has been overestimated.
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| 5. |
- Tamas, Ivica, et al.
(författare)
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50 million years of genomic stasis in endosymbiotic bacteria.
- 2002
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 296:5577, s. 2376-9
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Tidskriftsartikel (refereegranskat)abstract
- Comparison of two fully sequenced genomes of Buchnera aphidicola, the obligate endosymbionts of aphids, reveals the most extreme genome stability to date: no chromosome rearrangements or gene acquisitions have occurred in the past 50 to 70 million years, despite substantial sequence evolution and the inactivation and loss of individual genes. In contrast, the genomes of their closest free-living relatives, Escherichia coli and Salmonella spp., are more than 2000-fold more labile in content and gene order. The genomic stasis of B. aphidicola, likely attributable to the loss of phages, repeated sequences, and recA, indicates that B. aphidicola is no longer a source of ecological innovation for its hosts.
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