Bacterial Communities of Ixodes scapularis from Central Pennsylvania, USA

Insects. 2020 Oct 20;11(10):718. doi: 10.3390/insects11100718.


Native microbiota represent a potential resource for biocontrol of arthropod vectors. Ixodes scapularis is mostly inhabited by the endosymbiotic Rickettsia buchneri, but the composition of bacterial communities varies with life stage, fed status, and/or geographic location. We compared bacterial community diversity among I. scapularis populations sampled within a small geographic range in Central Pennsylvania. We collected and extracted DNA from ticks and sequenced amplicons of the eubacterial 16S rRNA gene from individuals and pooled samples. We then used taxon-specific PCR and/or qPCR to confirm the abundance or infection frequency of select pathogenic and symbiotic bacteria. Bacterial communities were more diverse in pools of males than females and the most abundant taxon was Rickettsia buchneri followed by Coxiellaceae (confirmed by sequencing as an unknown Rickettsiella species). High Rickettsiella titers in pools were likely due to a few heavily infected males. We determined that the infection frequency of Borrelia burgdorferi ranged from 20 to 75%. Titers of Anaplasma phagocytophilum were significantly different between sexes. Amplicon-based bacterial 16S sequencing is a powerful tool for establishing the baseline community diversity and focusing hypotheses for targeted experiments, but care should be taken not to overinterpret data based on too few individuals. We identified intracellular bacterial candidates that may be useful as targets for manipulation.

Keywords: Anaplasma; Borrelia; Ixodes scapularis; Rickettsia; Rickettsiella; microbiome; pathogens; symbiotic bacteria.