|Transmission electron micrograph of Wolbachia within an insect cell.Credit:Public Library of Science / Scott O'Neill|
Transmission electron micrograph of Wolbachia within an insect cell.
Credit:Public Library of Science / Scott O'Neill
Wolbachia is a genus of inherited bacterium which infects arthropod species, including a high proportion of insects. It is one of the world's most common parasitic microbes and is potentially the most common reproductive parasite in the biosphere, for example more than 16% of neotropical insect species carry this bacterium.
Association with disease
Outside of Insecta, Wolbachia infects a variety of isopod species, spiders, mites, and many species of filarial nematodes (a type of parasitic worm), including those causing onchocerciasis ("River Blindness") and elephantiasis in humans as well as heart worms in dogs. Not only are these disease-causing filarial infected with Wolbachia, but Wolbachia seem to play an inordinate role in these diseases. A large part of the pathogenicity of filarial nematodes is due to host immune response toward their Wolbachia. Elimination of Wolbachia from filarial nematodes generally results in either death or sterility (Hoerauf et al. 2003). Consequently, current strategies for control of filarial nematode diseases include elimination of Wolbachia via the simple doxycycline antibiotic rather than far more toxic anti-nematode medications (Outland 2005, Taylor et al. 2005).
Role in sexual differentiation of hosts
Within arthropods, Wolbachia is notable for significantly altering the reproductive capabilities of its hosts. These bacteria can infect many different types of organs, but are most notable for the infections of the testes and ovaries of their hosts.
Wolbachia are known to cause four different phenotypes:
- Male killing (death of infected males). This allows related infected females to be more likely to survive and reproduce.
- feminization (infected males develop as females or infertile pseudo-females)
- parthenogenesis(reproduction of infected females without males) and
- Cytoplasmic incompatibility (the inability of Wolbachia-infected males to successfully reproduce with uninfected females or females infected with another Wolbachia strain). This has the advantage of making the Wolbachia strain more likely to become prevalent as opposed to other strains of Wolbachia. This can have the additional result of making Wolbachia more common as a whole.
Wolbachia are present in mature eggs, but not mature sperm. Only infected females pass the infection on to their offspring. It is thought that the phenotypes caused by Wolbachia, especially cytoplasmic incompatibility, may be important in promoting speciation.  Wolbachia can also cause misleading results in molecular cladistical analyses (Johnstone & Hurst 1996).
A 2007 paper published in Science reports that a complete copy of the Wolbachia genome can be found within the genome of the fruit fly Drosophila ananassae and that Wolbachia appeared to have transmitted large segments of its genome into at least 7 other species.
|Wikinews has related news: Large scale gene transfer between single-celled and multicellular organisms reported|
- Werren JH, Guo L, Windsor DW. 1995. Distribution of Wolbachia in neotropical arthropods. Proc. R. Soc. London Ser. B 262:147–204
- Zimmer, Carl (2001). "Wolbachia: A Tale of Sex and Survival". Science. 292 (5519): 1093–1095. doi:10.1126/science.292.5519.1093. ISSN 0036-8075.
- Bordenstein, S. (2001). "Wolbachia-induced incompatibility precedes other hybrid incompatibilities in Nasonia". Nature. 409 (6821): 707–710. doi:10.1038/35055543. ISSN 0028-0836. Unknown parameter
- M. Hertig & S. B. Wolbach (1924). "Studies on Rickettsia-like microorganisms in insects". Journal of Medical Research. 44: 329&ndash, 374.
- Wu M; et al. (2004). "Phylogenomics of the reproductive parasite Wolbachia pipientis wMel: a streamlined genome overrun by mobile genetic elements". PLoS Biology. 2 (3): E69. Unknown parameter
- Foster J; et al. (2005). "The Wolbachia genome of Brugia malayi: endosymbiont evolution within a human pathogenic nematode". PLoS Biology. 3 (4): e121. Unknown parameter
|note=ignored (help); Unknown parameter
- Dunning Hotopp, JC; et al. (August 30, 2007). "Widespread Lateral Gene Transfer from Intracellular Bacteria to Multicellular Eukaryotes" (PDF). Science.
- Hoerauf, A. (2003). "Doxycycline as a novel strategy against bancroftian filariasis - depletion of Wolbachia endosymbionts from Wuchereria bancrofti and stop of microfilaria production". Medical Microbiology and Immunology. 192 (4): 211–216. doi:10.1007/s00430-002-0174-6. PMID 12684759. Unknown parameter
- Johnstone, Rufus A. (1996). "Maternally inherited male-killing microorganisms may confound interpretation of mitochondrial DNA variability". Biological Journal of the Linnean Society. 58 (4): 453–470. ISSN 0024-4066. Unknown parameter
- Taylor, M. J. (2005). "Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomised placebo-controlled trial". Lancet. 365 (9477): 2116–2121. doi:10.1016/S0140-6736(05)66591-9. ISSN 0140-6736. PMID 15964448. Unknown parameter
- Werren, J. H. (1997). "Biology of Wolbachia" (PDF). Annual Review of Entomology. 42: 587–609. doi:10.1146/annurev.ento.42.1.587. ISSN 0066-4170.