Adaptive restructuring of the microbiota promotes overwintering survival of the tick Dermacentor silvarum.

backgroundDermacentor silvarum is a medically important tick species in temperate regions of Asia that must survive prolonged cold exposure during winter. However, the impact of low-temperature stress on its microbial community and the potential functional implications for overwintering remain poorly understood.

methodsAdult ticks of D. silvarum were subjected to controlled low-temperature treatments (8, 4, 0, and -4 °C) for 7 days, with ticks maintained at 27 °C serving as controls. The bacterial 16S rRNA (V4 region) and fungal ITS1 regions were amplified and sequenced using the Illumina NovaSeq PE250 platform. Bioinformatics analyses were performed to assess microbial diversity, community composition, and predicted functional profiles.

resultsCold exposure significantly altered both bacterial and fungal community structures, increasing overall microbial diversity. Proteobacteria and Actinobacteriota dominated the bacterial assemblages, whereas the Ascomycota and Basidiomycota were the predominant fungal phyla. A marked enrichment of psychrotolerant and metabolically versatile genera, including Pseudomonas, Sphingomonas, and Trichosporon, alongside a decline in the nutrient-provisioning symbiont Coxiella were observed in cold-treated ticks. Functional prediction suggested that the enriched taxa are potentially involved in antioxidative defense, cryoprotectant biosynthesis, membrane stabilization, and detoxification processes.

conclusionsThe results demonstrate that low temperature drives a comprehensive reorganization of the microbiota in D. silvarum. The increase in psychrotolerant and detoxifying microbes likely reflects an adaptive host-microbe interaction that enhances tolerance to cold, oxidative, and osmotic stress, thereby promoting overwinter survival of the ticks. These findings provide new insights into the ecological resilience of tick-associated microbiomes and the symbiotic mechanisms underlying vector adaptation to climatic challenges.