Changes in the microbiota of Blattella germanica by antibiotic perturbations: the effect of rifampicin

Eukaryotes have established symbiotic relationship with microorganisms to allow them to fulfill the functions that they cannot perform alone. In the German cockroach Blattella germanica, the obligate endosymbiont Blattabacterium coexists with a rich gut microbiota. Although the transmission of Blattabacterium is vertical, how the gut microbiota colonizes newborn individuals is still unknown. In this study, we have treated B. germanica populations with rifampicin, a broad-spectrum antibiotic, during two generations and analyzed gut bacterial composition and the Blattabacterium load in control and rifampicin-treated populations. A drastic rifampicin effect on the gut microbiota composition was detected, which is recovered in the second generation when the antibiotic was not added to the diet. Furthermore, we observed that bacterial species present in the diet, and particularly in the feces contribute significantly to the establishment of the gut microbiota. Finally, Blattabacterium was not affected by the antibiotic treatment during the first generation but underwent a drastic reduction from the first to the second generation, when the Blattabacterium moves freely to invade the embryos and is strongly exposed to the effects of rifampicin.