Symbiotic bacteria used in disease control host an unexpected diversity of mobile genetic elements

What is it about?

The bacterium Wolbachia is widely found in arthropods (such as insects and spiders), where it is passed down from mothers to their offspring. It can help protect these animals from viral pathogens and can also cause changes in their reproduction that make it easier for Wolbachia to spread. Health interventions are now using Wolbachia to curb the transmission of viruses such as dengue and Zika by introducing the bacterium into wild mosquito populations. In this study, we sequenced the genome of a strain of Wolbachia that is naturally present in the Asian tiger mosquito and found that it carries two extrachromosomal genetic elements called plasmids. By reanalysing public genome databases, we also showed that plasmids are much more common in Wolbachia than previously thought and often carry genes that may allow them to move between different Wolbachia. Some plasmids may also carry genes important for Wolbachia's relationship with its host and its ability to manipulate reproduction. These findings will help better understand Wolbachia and develop new ways to manipulate its genome for addressing fundamental questions in biology and for disease control.

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Photo by Shardar Tarikul Islam on Unsplash

Photo by Shardar Tarikul Islam on Unsplash

Why is it important?

Our study has important implications for human applications currently using Wolbachia to limit the spread of medically-important viruses transmitted by mosquitoes. In particular, Wolbachia-associated plasmids could inspire new methods to manipulate the bacterium and improve its properties, which could lead to more effective disease control strategies in the future.