Bacterial community in digestive and excretory organs of cicada S. yangi

Symbiotic associations with microbes represent major driving forces of the insect host evolution by allowing for the expansion into new ecological niches and subsequent lineage diversification. Although bacteriocyte-associated symbionts have been reported in cicadas, limited studies on the gut bacterial communities in this lineage have been conducted. Here, we characterized the bacterial communities in the salivary glands, each parts of gut and Malpighian tubules of the cicada Subpsaltria yangi based on two populations occurring in Helan Mountains (HM) and Hancheng (HC), which feed on different host plants, Ziziphus jujuba var. spinosa and Ephedra lepidosperma, respectively. Results show that the bacterial diversity has no significant differences among the salivary glands, different parts of the gut and Malpighian tubules. A shared core microbiota in S. yangi of both populations was simple and consisted mostly of three bacterial genera: Meiothermus, the primary endosymbiont Candidatus Sulcia, and Halomonas. Differences in relative abundance were detected on the shared core microbiome, but for both populations, they were mainly harbored in the conical segment and rectum. In addition, the abundance of Meiothermus and Ca. Sulcia in samples of the HC population was significantly higher than that in the corresponding organs of the HM population. NMDS analysis revealed that the bacteria of digestive and excretory organs clustered weakly by populations, suggesting diet was not the main determinant for gut bacterial communities in S. yangi. When compared with the core microbiota of two phylogenetically distant cicada species Hyalessa maculaticollis and Meimuna mongolica, the core microbiota in digestive and excretory organs of S. yangi was totally different. Pseudomonas, Enterobacter and Pantoea are the core microbiota of H. maculaticollis and M. mongolica. This suggests that the core microbiota in digestive and excretory organs of cicadas is closely related with the phylogeny of cicadas, but the bacterial community could be influenced by the diet slightly within a cicada species, which potentially reflecting the co-evolutionary interactions between cicada host and gut microbes. The description of bacterial community in digestive and related excretory organs of cicadas can contribute to a more comprehensive understanding of the symbiosis of sap-feeding insects and the microbes.