Influential Insider: <i>Wolbachia</i>, an Intracellular Symbiont, Manipulates Bacterial Diversity in Its Insect Host

Facultative intracellular symbionts like the α-proteobacteria Wolbachia influence their insect host phenotype but little is known about how much they affect their host microbiota. Here, we quantified the impact of Wolbachia infection on the bacterial community of the cabbage root fly Delia radicum by comparing the microbiota of Wolbachia-free and infected adult flies of both sexes. We used high-throughput DNA sequencing (Illumina MiSeq, 16S rRNA, V5-V7 region) and performed a community and a network analysis. In both sexes, Wolbachia infection significantly decreased the diversity of D. radicum bacterial communities and modified their structure and composition by reducing abundance in some taxa but increasing it in others. Infection by Wolbachia was negatively correlated to 8 bacteria genera (Erwinia was the most impacted), and positively correlated to Providencia and Serratia. We suggest that Wolbachia might antagonize Erwinia for being entomopathogenic (and potentially intracellular), but would favor Providencia and Serratia because they might protect the host against chemical plant defenses. Although they might seem prisoners in a cell, endocellular symbionts can impact the whole microbiota of their host, hence its extended phenotype, which provides them with a way to interact with the outside world