Molecular and electron microscopic identification of Wolbachia in Culex pipiens complex populations from the Upper Rhine Valley, Germany, and Cebu City, Philippines

We detected Wolbachia infections in Culex pipiens complex mosquitoes from the Upper Rhine Valley, Germany, and Cebu City, Philippines, with the use of polymerase chain reaction (PCR) amplification of the 16S rDNA of the bacteria and further confirmation by electron microscopy. Species of 5 different autogenous and anautogenous populations of Culex pipiens from Germany and 1 population of Culex quinquefasciatus from the Philippines were used in this study. Larvae were sampled from different localities and reared to the adult stage for further processing. Whole adult males and the heads of adult females were processed by PCR, whereas the abdomens of females were used for electron microscopic study when an infection was detected by PCR. All Culex populations assayed by PCR showed infection of Wolbachia at rates between 10 and 100%. Females from different populations exhibited higher infection rates than did the males, and, likewise, Cx. pipiens populations that were autogenous showed higher infection rates of Wolbachia than did anautogenous individuals. In Cx. quinquefasciatus populations, males were infected at 33.33% and females, only 10%. We studied the ultrastructure of Wolbachia in the ovaries of species belonging to Cx. pipiens complex by means of transmission electron microscopy. The bacteria exhibited typical morphology for Wolbachia with 3 enveloping membranes.