uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Comparative Genomics of Wolbachia and the Bacterial Species Concept
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
Show others and affiliations
2013 (English)In: PLOS Genetics, ISSN 1553-7404, Vol. 9, no 4, e1003381- p.Article in journal (Refereed) Published
Abstract [en]

The importance of host-specialization to speciation processes in obligate host-associated bacteria is well known, as is also the ability of recombination to generate cohesion in bacterial populations. However, whether divergent strains of highly recombining intracellular bacteria, such as Wolbachia, can maintain their genetic distinctness when infecting the same host is not known. We first developed a protocol for the genome sequencing of uncultivable endosymbionts. Using this method, we have sequenced the complete genomes of the Wolbachia strains wHa and wNo, which occur as natural double infections in Drosophila simulans populations on the Seychelles and in New Caledonia. Taxonomically, wHa belong to supergroup A and wNo to supergroup B. A comparative genomics study including additional strains supported the supergroup classification scheme and revealed 24 and 33 group-specific genes, putatively involved in host-adaptation processes. Recombination frequencies were high for strains of the same supergroup despite different host-preference patterns, leading to genomic cohesion. The inferred recombination fragments for strains of different supergroups were of short sizes, and the genomes of the co-infecting Wolbachia strains wHa and wNo were not more similar to each other and did not share more genes than other A- and B-group strains that infect different hosts. We conclude that Wolbachia strains of supergroup A and B represent genetically distinct clades, and that strains of different supergroups can co-exist in the same arthropod host without converging into the same species. This suggests that the supergroups are irreversibly separated and that barriers other than host-specialization are able to maintain distinct clades in recombining endosymbiont populations. Acquiring a good knowledge of the barriers to genetic exchange in Wolbachia will advance our understanding of how endosymbiont communities are constructed from vertically and horizontally transmitted genes.

Place, publisher, year, edition, pages
2013. Vol. 9, no 4, e1003381- p.
National Category
URN: urn:nbn:se:uu:diva-200821DOI: 10.1371/journal.pgen.1003381ISI: 000318073300004OAI: oai:DiVA.org:uu-200821DiVA: diva2:625097
Available from: 2013-06-04 Created: 2013-06-04 Last updated: 2014-04-29Bibliographically approved
In thesis
1. Genome Evolution and Niche Differentiation of Bacterial Endosymbionts
Open this publication in new window or tab >>Genome Evolution and Niche Differentiation of Bacterial Endosymbionts
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Most animals contain chronic microbial infections that inflict no harm on their hosts. Recently, the gut microflora of humans and other animals have been characterized. However, little is known about the forces that shape the diversity of these bacterial communities. In this work, comparative genomics was used to investigate the evolutionary dynamics of host-adapted bacterial communities, using Wolbachia infecting arthropods and Lactobacteria infecting bees as the main model systems.

Wolbachia are maternally inherited bacteria that cause reproductive disorders in arthropods, such as feminization, male killing and parthenogenesis. These bacteria are difficult to study because they cannot be cultivated outside their hosts. We have developed a novel protocol employing multiple displacement amplification to isolate and sequence their genomes. Taxonomically, Wolbachia is classified into different supergroups. We have sequenced the genomes of Wolbachia strain wHa and wNo that belong to supergroup A and B, respectively, and are present as a double-infection in the fruit-fly Drosophila simulans. Together with previously published genomes, a supergroup comparison of strains belonging to supergroups A and B indicated rampant homologous recombination between strains that belong to the same supergroup but were isolated from different hosts. In contrast, we observed little recombination between strains of different supergroups that infect the same host.

Likewise, phylogenetically distinct members of Lactic acid bacteria co-exist in the gut of the honeybee, Apis mellifera, without transfer of genes between phylotypes. Nor did we find any evidence of co-diversification between symbionts and hosts, as inferred from a study of 13 genomes of Lactobacillus kunkeei isolated from diverse bee species and different geographic origins. Although Lactobacillus kunkeii is the most frequently isolated strain from the honey stomach, we hypothesize that the primary niche is the beebread where the bacteria are likely to contribute to the fermentation process.

In the human gut, the microbial community has been shown to interact with the immune system, and likewise the microbial communities associated with insects are thought to affect the health of their host. Therefore, a better understanding of the role and evolution of endosymbiotic communities is important for developing strategies to control the health of their hosts.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 57 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1121
niche, habitat, endosymbiont, gut microbiome, honey bee, Wolbachia, comparative, genomics
National Category
Evolutionary Biology
urn:nbn:se:uu:diva-217724 (URN)978-91-554-8872-7 (ISBN)
External cooperation:
Public defence
2014-03-21, B42, Husargatan 3, Uppsala, 10:15 (English)
Available from: 2014-02-27 Created: 2014-02-04 Last updated: 2016-08-26Bibliographically approved

Open Access in DiVA

fulltext(1759 kB)279 downloads
File information
File name FULLTEXT01.pdfFile size 1759 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Ellegaard, Kirsten MarenKlasson, LisaNäslund, KristinaAndersson, Siv G. E.
By organisation
Molecular EvolutionScience for Life Laboratory, SciLifeLab
In the same journal
PLOS Genetics

Search outside of DiVA

GoogleGoogle Scholar
Total: 279 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 570 hits
ReferencesLink to record
Permanent link

Direct link