Wolbachia is no ordinary bacterium. This parasitic microbe lives inside the cells of over 40% of insect species and hacks the biology of fruit flies by making them friskier. This boosts its chances of spreading — one mating at a time.
“We found statistically significant differences in the number of matings and rematings an infected female undergoes compared with uninfected females,” says Dr Timothy Karr, a Research Associate in Neurodegenerative Disease at Arizona State University.
He’s been studying Wolbachia for decades, which is most well-known for rendering male insects sterile if they mate with an uninfected female. “Whereas an infected female mating with an infected male is a compatible cross, and the bacterium is propagated to the population via the female egg.”
It’s for this reason Wolbachia has already been used to lessen the spread of mosquito-borne diseases like dengue and Zika. Additionally, the bacteria interfere with the mosquitoes’ ability to transmit viruses to humans by outcompeting them inside their mosquito hosts. This dual effect helps lower both the number of mosquitoes and the risk of disease transmission.
But now, Karr’s team has shown that Wolbachia even colonises areas of the female fruit fly brain responsible for decision-making and sensory perception - boosting their desire to mate and, in turn, increasing the spread of the bacterium itself.
By comparing brain protein levels between infected and uninfected flies, they found more than 170 proteins had changed, but three stood out. Protein Obp99b (linked to smell), protein TfAP-2 (a gene regulator), and a receptor protein called mGluR, which helps process sensory signals in the brain. All three are known to be involved in behaviours linked to mating.
And in a major breakthrough in understanding how parasites can manipulate host behaviour from the inside out, the team also showed that lowering mGluR in uninfected females made them behave like the infected ones – mating more and producing more eggs.
Their study, published in Cell Reports, opens doors to practical applications beyond the control of diseases deadly to humans. Understanding exactly how Wolbachia alters insect behaviour means researchers might be able to design more targeted pest-control methods – ones that are safer and longer-lasting than chemical pesticides.
This study is just the beginning. By using an AI system called AlphaFold, the team identified over 700 bacterial proteins in the brain – some of which may help Wolbachia produce essential amino acids for their insect hosts. This hints at a possible mutual benefit, similar to how chloroplasts and mitochondria – the powerhouses of our cells – evolved from ancient bacteria that once invaded cells but later became vital partners, a process known as the endosymbiotic theory. It’s like watching evolution in action.
In other words, what began as a parasitic hitchhiker may be evolving into a biological partner - moving from mind control to mutual gain. So next time you see a fruit fly buzzing around, remember, it might not be flying solo. It could be an evolving fly that caught the love bug.
