Tick microbiomes revealed by Batch Learning Self-Organizing Maps (BLSOMs)
Tick can transmit a variety of viral, bacterial and protozoal pathogens, which are often zoonotic. The increasing number of novel tick-borne pathogens has been reported during recent decades. The aim of this study was to reveal a diversity of tick microbiomes which may contain as-yet unidentified pathogens using a metagenomic approach. Seven tick species (both field-collected and laboratory-reared) were used in the present study. Purified bacteria-enriched fraction prepared from tick homogenate was subjected to DNA extraction and pyrosequencing after whole genome amplification. Resulting sequence reads were phylotyped using a Batch Learning Self-Organizing Map (BLSOM) program, which allowed phylogenetic estimation based on the similarity of oligonucleotide frequencies, and functionally annotated by BLASTX similarity searches. We showed that ticks harboured a variety of bacteria including those previously associated with human and animal diseases such as genera Anaplasma, Bartonella, Borrelia, Ehrlichia, Francisella, and Rickettsia. Gene sequences associated with bacterial pathogenesis were identified and were suspected to be introduced through horizontal gene transfer. In conclusion, our efforts to construct a database of tick microbes may lead to the empowerment to predict emerging tick-borne diseases. A comprehensive understanding of the tick microbiomes will also be useful to understand tick biology including vector competency and interactions with pathogens.