Tetracycline reduces feeding and reproduction of the parthenogenetic springtail, Folsomia candida

Treatment with tetracycline or rifampicin to eliminate the obligate intracellular bacterium, Wolbachia pipientis, provides an important tool for validating Wolbachia’s diverse effects on arthropod reproduction, including cytoplasmic incompatibility, feminization, male killing and parthenogenesis. For the soil collembolan, Folsomia candida (Entomobryomorpha: Isotomidae) efforts to establish the role of Wolbachia in parthenogenesis using tetracycline have been ambiguous, possibly reflecting variation in overall experimental design, mode of antibiotic application and duration of treatment. By maintaining F. candida populations on agar plates containing dissolved antibiotics we show that the EC ₅₀ (effective concentration for 50% reduction in biomass) for tetracycline is 50-fold higher than for rifampicin. Experiments with the fluorescent dye rhodamine further show that tetracycline deters feeding. Using individual Collembola, we show that reproductively mature F. candida survive more than 60 days exposure to tetracycline at concentrations 4-fold higher than the EC ₅₀ and that its effect on egg production is reversible, consistent with persistence of Wolbachia during tetracycline treatment. As has been shown with other microbes, our results suggest that in F. candida, Wolbachia survives antibiotic exposure by entering a metabolically dormant persister state, from which it can recover under favorable conditions. This possibility is of particular interest because persister cells are induced by toxin-antitoxin (TA) gene pairs, which have recently been associated with Wolbachia-induced cytoplasmic incompatibility in Culex pipiens mosquitoes.