Wolbachia are members of the Rickettsia, a diverse group of intracellular bacteria that comprises bacteria with parasitic, mutualistic and commensal relationships with their hosts. Typical Rickettsia have life cycles that include an invertebrate vector and mammalian host. However, unlike its close relatives, Wolbachia does not routinely infect vertebrates. Wolbachia species have attracted considerable interest in the past decade primarily because of their abundance, fascinating effects on their hosts and their potential in pest and disease vector control (Wolbachia: master manipulators of invertebrate biology. 2008 Nature Reviews Microbiology 6, 741-751).
Wolbachia have small genomes (1-2 Mb) that are within the size range of the other Rickettsia. Until the early 1990s, Wolbachia were considered to be rare, but with the advent of PCR, Wolbachia were found to be widespread and are in fact common in insects and other arthropods, as well as in nematodes. Recent work estimates that over 65% of insect species harbour Wolbachia, making it among the most abundant intracellular bacterial genus so far discovered, infecting over a million insect species alone.
Together with their widespread distribution, another interesting feature of Wolbachia is the various host manipulations they induce. The effects of Wolbachia infection include: feminization of genetic males; parthenogenetic induction, resulting in the development of unfertilized eggs; the killing of male progeny from infected females; and sperm–egg incompatibility. Each of these reproductive alterations helps the bacterium by enhancing the production of infected female hosts, and this is referred to as reproductive parasitism. Whether Wolbachia have a role in accelerating the evolution of their hosts is a controversial question, but there is good evidence that parthenogenesis-inducing bacteria have led to the evolution of parthenogenetic insect species.
Considerable progress in understanding the biology of Wolbachia has been made in the past ten years. However, important questions still remain, including: how do Wolbachia manipulate host reproduction; how is the abundance and distribution of Wolbachia maintained globally; can Wolbachia be effectively used in disease control; do Wolbachia have important roles in the evolution of their hosts; and do Wolbachia accelerate the rates of speciation in invertebrates and contribute to novel gene acquisition.
- Parasite genomes
- Malaria Researchers Identify New Mosquito Virus
- Jumping Genes, Wolbachia Style
- PubMed: Wolbachia