Bacterial Communities of Ixodes scapularis from Central Pennsylvania, USA.

Abstract

Simple SummaryThe blacklegged tick, Ixodes scapularis, is one of the most important arthropod vectors in the United States, most notably as the vector of the bacteria Borrelia burgdorferi, which causes Lyme disease. In addition to harboring pathogenic microorganisms, ticks are also populated by bacteria that do not cause disease (nonpathogens). Nonpathogenic bacteria may represent potential biological control agents. Before investigating whether nonpathogenic bacteria can be used to block pathogen transmission or manipulate tick biology, we need first to determine what bacteria are present and in what abundance. We used microbiome sequencing to compare community diversity between sexes and populations and found higher diversity in males than females. We then used PCR assays to confirm the abundance or infection frequency of select pathogenic and symbiotic bacteria. Further studies are needed to examine whether any of the identified nonpathogenic bacteria can affect tick biology or pathogen transmission.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.