Recombination in Wolbachia Endosymbionts of Filarial Nematodes?

摘要

We read with interest the recent paper by Ros and col- leagues (8) reporting recombination in the citrate synthase gene (gltA) from Wolbachia endosymbionts of filarial nema- todes that belong to Wolbachia supergroups C and D. We were intrigued by this observation, since unlike the mostly parasitic relationship between Wolbachia endosymbionts and arthropod hosts, where coinfection with two or more Wolbachia strains and genetic exchange via recombination are common (1, 9), neither phenomenon had been detected previously for Wolba- chia strains which mutualistically colonize nematodes (2, 5, 6). Furthermore, the nematode hosts of the Wolbachia strains implicated in the recombination event infect different mam- malian hosts and are transmitted by distinct insect vectors. Since the phylogeny of filarial nematodes appears highly con- gruent with that of their Wolbachia endosymbionts, indicative of long, stable coevolution (3), and horizontal transfers be- tween nematode hosts are not known, it is difficult to under- stand how such recombination might have occurred.