Genome sequencing and comparative analysis of Wolbachia strain wAlbA reveals Wolbachia-associated plasmids are common

Wolbachia is the most common bacterial symbiont of arthropods, being found in about half of terrestrial species around the globe. It is transmitted from mother to offspring, can spread rapidly by inducing various forms of reproductive parasitism and often provides protection against viral pathogens. These properties are being harnessed by disease control interventions introducing Wolbachia into wild populations of virus-transmitting mosquitoes. Here we sequenced the genome of wAlbA, a strain of the symbiont naturally found in Aedes albopictus mosquitoes and demonstrate that it is associated with two extrachromosomal plasmid elements. We then reanalysed publicly available sequencing data and found that plasmids are much more common in Wolbachia than previously thought. Some of them carry genes potentially important for symbiosis and reproductive manipulation as well as phage-like genes that may allow them to move between symbiont strains. Our findings provide a new framework for studying Wolbachia and will help the future development of genetic tools for manipulating symbiont genomes.

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