Comparative analysis of microbial communities associated with bacteriomes, reproductive organs and eggs of the cicada Subpsaltria yangi.

Plant sap-feeding insects of Hemiptera often form intimate symbioses with microbes to obtain nutrients. The cicada Subpsaltria yangi is the only species of the subfamily Tettigadinae known from China. Using high-throughput sequencing combined with fluorescence in situ hybridization analysis, we characterize the bacterial composition of the bacteriomes, testes, ovaries and eggs of two representative populations of this species which occur in different habitats and feed on different plant hosts. In both populations, the bacterial community diversity in the testes was significantly higher than that in other tissues. The obligate endosymbiont Candidatus Sulcia muelleri was observed in all samples and was dominant in the bacteriomes, ovaries and eggs. The usual co-resident endosymbiont Candidatus Hodgkinia cicadicola found in some other cicadas was not detected. Instead, a novel Rhizobiales bacterium which shows a ~ 81% 16S rDNA similarity to Ca. Hodgkinia cicadicola was detected. Given that the genome of Ca. Hodgkinia cicadicola exhibits rapid evolution, it is possible that this novel Rhizobiales bacterium is a related endosymbiont with beneficial trophic functions similar to that of Ca. Hodgkinia cicadicola hosted by several certain other cicadas. The presence of the novel Rhizobiales species in other cicadas and its involvement with the adaptive evolution of related cicada hosts require further investigation. Discrepancy of bacterial communities associated with testes between the two populations may be closely related to the geographic isolation and divergence of habitats and host plants. Our results are informative for further studies of evolutionary divergence of related endosymbionts hosted in cicadas.