Sexual and regional differences in the microbiome and functional metagenome of the lone star tick, Amblyomma americanum

Ticks are important vectors of pathogens that cause disease in humans and domestic and wild animals. Understanding how microbes within ticks interact among themselves and with their tick host is a significant step in controlling diseases vectored by ticks and other arthropods. We used Illumina sequencing of the 16S rRNA bacterial gene to characterize the diversity and composition of the microbiome of the lone star tick (Amblyomma americanum), an aggressive tick in the United States that is expanding its geographic range both westward and northward. Specifically, we examined differences in microbial community structure and metabolic pathways between two regions at the boundary of the lone star tick’s current range, between sexes, and between wild and laboratory-reared tick populations. Geographic region and sex strongly influence alpha diversity, beta diversity, the relative abundance of particular taxa, and the prevalence of pathogens. Analyses of phylogenetic structure suggest that bacterial community assembly is shaped not by competitive exclusion, but by environmental filtering related to tick physiology—particularly in females. Additionally, we show that distinct taxonomic profiles of the tick microbiome lead to distinct functional profiles between the sexes, highlighting important vitamin and heme metabolic pathways that are significantly more abundant in the metagenomes of female ticks. This study integrates taxonomic profiling and predictive functional metagenomics to elucidate important associations between ticks and their microbes. It is the largest tick microbiome investigation to date based on next-generation sequencing of the 16S rRNA bacterial gene, and it reveals that both sex and geographic region affect various aspects of the microbiome and functional metagenome of A. americanum. Discovering the mechanisms through which microbes help ticks can make dysbiosis a potential strategy for tick control.