ferrinetal_Interactiveeffectsofwarmingabandnanoonthegutmicrobiomeofsoilcollembola

Nanoplastics and antibiotics are among the most abundant chemical pollutants of soils, but their interplay with global warming remains poorly understood. Finding ways to better assess the impact of these xenobiotics in soils is mandatory to protect the biodiversity of soil organisms and ecosystem services. The springtail Folsomia candida (Class Collembola) is a standard model for ecotoxicological assays with potential as a bioindicator of soil 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 in microcosms to either nanoplastics or an antibiotic under two temperatures. The antibiotic treatment consisted of colistin addition (50 g·kg-1 of dry soil), and the nanoplastic treatment consisted of polystyrene particles 0.044 µm in diameter (0.1 g·kg-1 of dry soil). Both treatments were incubated at 20 and 22 °C for two months, and their bacterial gut microbiomes were then sequenced. Warming strongly interacted with the impact of both xenobiotics on F. candida gut microbiome. Exposure to nanoplastics at 20 °C decreased the abundance of the most dominant bacterial phyla and families, and decreased the evenness of the gut microbiome. Warming of +2 °C, however, increased the abundances and evenness of the dominant families. Surprisingly, Gram-negative 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 response of the gut microbiome to the particles. Our results also indicated that warming was a major driver that modulated 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.