Interactive effects of warming, antibiotics, and nanoplastics on the gut microbiome of the collembolan Folsomia candida

Nanoplastics and antibiotics are among the most abundant chemical pollutants of soils, but their interplay with global warming remains poorly understood. The springtail Folsomia candida (Class Collembola) is a standard model for ecotoxicological assays with potential as a bioindicator of xenobiotics. Little is known, however, about their gut microbiome and how it might respond to warming and these pollutants. We exposed populations of F. candida to nanoplastics and antibiotic under two temperatures. The antibiotic treatment consisted of colistin addition, and the nanoplastic treatment consisted of polystyrene particles (50 mg kg−1 and 0.1 g kg−1 of dry soil, respectively). Both treatments were incubated at 20 and 22 °C for two months, and the bacterial gut microbiomes of springtails were then sequenced. Exposure to nanoplastics at 20 °C decreased the abundance of the dominant bacterial phyla and families, and decreased the evenness of the gut microbiome. At 22 °C, however, the abundances and evenness of the dominant families increased. Surprisingly, Gramnegative bacteria targeted by colistin were not globally affected. And at genus-level, the endosymbiont Wolbachia controlled the compositional shifts under nanoplastic addition, potentially driving the gut microbiome. Our results also indicated that warming was a major driver modulating the impacts of the antibiotic and nanoplastics. We illustrate how the gut microbiomes of springtails are sensitive communities responsive to xenobiotics and provide evidence of the need to combine multiple factors of global change operating simultaneously if we are to understand the responses of communities of soil arthropods and their microbiomes.