Phenotypic Response of Wolbachia pipientis in a Cell-Free Medium.

Wolbachia, an obligate intracellular bacterium estimated to infect millions of arthropod species worldwide, is currently being utilized in novel control strategies to limit the transmission of Dengue and Zika viruses. A limitation for Wolbachia-based control approaches is the difficulty of transferring Wolbachia to novel hosts and the lack of tools for the genetic transformation of Wolbachia due to the inability to culture Wolbachia outside the insect host cell in an axenic media. Here, we applied extracellular Wolbachia to phenotypic microarrays to measure the metabolic response of Wolbachia in media formulations with different pH levels and supplementation with Casamino acids. Results suggested a pH of 6.5-6.8 and showed that the supplementation of 1 mg/mL casamino acids increased the survival and longevity of Wolbachia in an axenic medium. In addition, phenotypic microarrays are a useful tool to measure the phenotypic response of Wolbachia under different media conditions, as well as determine specific components that may be required for an axenic medium. This study is an initial step toward the development of a potential Wolbachia axenic culture system.

Cryptic Wolbachia (Rickettsiales: Rickettsiaceae) Detection and Prevalence in Culicoides (Diptera: Ceratopogonidae) Midge Populations in the United States.

Culicoides midges vector numerous veterinary and human pathogens. Many of these diseases lack effective therapeutic treatments or vaccines to limit transmission. The only effective approach to limit disease transmission is vector control. However, current vector control for Culicoides midges is complicated by the biology of many Culicoides species and is not always effective at reducing midge populations and impacting disease transmission. The endosymbiont Wolbachia pipientis Hertig may offer an alternative control approach to limit disease transmission and affect Culicoides populations. Here the detection of Wolbachia infections in nine species of Culicoides midges is reported. Infections were detected at low densities using qPCR. Wolbachia infections were confirmed with the sequencing of a partial region of the 16S gene. Fluorescence in situ hybridization of Culicoides sonorensis Wirth and Jones adults and dissected ovaries confirm the presence of Wolbachia infections in an important vector of Bluetongue and Epizootic hemorrhagic disease viruses. The presence of Wolbachia in Culicoides populations in the United States suggests the need for further investigation of Wolbachia as a strategy to limit transmission of diseases vectored by Culicoides midges.