Evolutionary microbial genomics: insights into bacterial host adaptation

• Published in: Nature reviews. Genetics Vol. 11; no. 7; pp. 465 - 475
• Main Authors: Toft, Christina, Andersson, Siv G. E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2010; Nature Publishing Group
• Subjects: 631/326/41/2529; 631/326/41/2530; Adaptation; Adaptation, Biological; Agriculture; Animal Genetics and Genomics; Animals; Bacteria; Bacteria - genetics; Biologi; Biological and medical sciences; Biological diversity; Biological Evolution; Biology; Biomedical and Life Sciences; Biomedicine; Cancer Research; Diverse techniques; Evolution; Flowers & plants; Fundamental and applied biological sciences. Psychology; Gene Function; Gene Transfer, Horizontal; Genetic aspects; Genetics of eukaryotes. Biological and molecular evolution; Genome, Bacterial; Genomes; Genomics; Host-bacteria relationships; Human Genetics; Humans; Lifestyles; Molecular and cellular biology; Mutualism; Mutualism (Biology); NATURAL SCIENCES; NATURVETENSKAP; Phylogenetics; review-article; Symbiosis; Sweden; Infection; Molecular evolution; Genomics; Bacteriosis; Bacteria; Review; Adaptation
• ISSN: 1471-0056; 1471-0064; 1471-0064
• DOI: 10.1038/nrg2798

Key Points The wealth of genome data for host-adapted bacteria have made it possible to re-examine and quantify the level of integration between bacteria and their hosts. For genera with multiple hosts there seems to be a correlation between host range, host population size and the repertoire of bacterial outer surface proteins. Shifts in bacterial lifestyle towards greater interaction with the host are mediated by mechanisms such as gain of new functions through horizontal gene transfer and duplication and functional divergence of existing genes. Bacteria from many different phyla have established relationships with animals, plants and invertebrates. Mutualistic relationships are mostly seen in invertebrates, suggesting that plants and animals present barriers to obligate mutualism that are difficult to overcome. Secretion systems in bacteria are essential for the interaction with their eukaryotic hosts. Horizontal gene transfer events, functional diversification and innovation through gene duplication of these systems have made it possible for bacteria to adapt to their host in various ways, giving rise to pathogenic or mutualistic relationships. Obligate mutualistic bacteria with highly eroded genomes have survived owing to selective pressure on the essential function they contribute to eukaryotic fitness. This contribution has resulted in intimate relationships, in which some bacteria have transferred their genes to the host nuclear genome or established consortia with other co-habiting symbionts for the benefit of the host. The recent sequencing of the genomes of diverse bacteria at different stages of host adaptation is leading to the revision of concepts in microbial evolutionary genomics that were based on studies of laboratory strains. New insights into genetic changes and selective pressures are emerging. Host-adapted bacteria include mutualists and pathogens of animals, plants and insects. Their study is therefore important for biotechnology, biodiversity and human health. The recent rapid expansion in bacterial genome data has provided insights into the adaptive, diversifying and reductive evolutionary processes that occur during host adaptation. The results have challenged many pre-existing concepts built from studies of laboratory bacterial strains. Furthermore, recent studies have revealed genetic changes associated with transitions from parasitism to mutualism and opened new research avenues to understand the functional reshaping of bacteria as they adapt to growth in the cytoplasm of a eukaryotic host.