A genus of Gram-negative bacteria that resemble Rickettsia (q.v.) and live as endosymbionts in many invertebrates (including nematodes, mites, spiders, crustaceans, and insects). Wolbachia are inherited maternally by transovarial transmission, and they often manipulate the reproductive behavior of their hosts. For example, in some insects the infecting Wolbachia secrete toxins that kill Y-bearing sperm, and female-biased sex ratios result. In a strain of the beetle Callosobruchus chinensis the X chromosome has been shown to contain a Wolbachia DNA fragment. This is about 11 kbp and contains 12 ORFs, somewhat more than 1% of the genome of the Wolbachia. The structure of the transferred segment is highly preserved which suggests that the transfer was recent. Wolbachia pipientis (wMel) is an obligate intracellular parasite of Drosophila melanogaster. A recent survey of cultures kept at the Bloomington Drosophila Stock Center at Indiana University found that 30% of the strains were infected with Wolbachia. The wMel genome consists of a 1,267,782 bp circle of DNA. It contains very high levels of repetitive DNA and mobile DNA elements. However, there is no evidence for recent lateral gene transfer between wMel and its Drosophila host. See Classification, Prokaryotae, Bacteria, Protobacteria; Chronology, 2002, Kondo et al.; horizontal transmission.
Subjects: Genetics and Genomics.