A couple of years ago, Australian postdoc Nate Lo was working at the University of Milan, looking for human pathogens in the tick species Ixodes ricinus, the main vector for Lyme disease. It was all routine until the day his PCR screening protocol revealed a novel 16S rRNA sequence. When his team took a tick apart to look for the new bug, they found it in the ovaries. And, when they looked closely at electron micrographs of infected ovarian tissues, they could see that the microbes were intracellular - living not in the cytoplasm of tick ova, but within their mitochondria.
"We'd never seen anything like this before," Lo says, as he opens the image files on his laptop on a rainy afternoon in Sydney. "They seem to get in between the inner and outer mitochondrial membranes and eat the mitochondria up. In the end you've just got this empty sack."
"It's a very novel observation," says Scott O'Neill, a specialist in invertebrate endosymbionts and head of the School of Integrative Science at the University of Queensland, who wasn't involved in the research. O'Neill, whose recent work has focused on the bacterium Wolbachia, says he wasn't aware of any other bacteria that live inside mitochondria. "It's pretty surprising to see a bacterial species living inside the mitochondrion, which itself was a bacterium," he says. "I think it is significant." Bill Ballard, a mitochondrial specialist from the University of New South Wales, agrees. "This is, as far as I know, the first [bacterium] that actually infects within the mitochondria," he says. "It's a pretty cool paper."
Lo's newly found organism doesn't seem to have any negative effects on the ticks. "About half the mitochondria don't get infected," he says, "so perhaps they are only destroying old ones. We don't really know what's going on."
Lo moved to his current post at the University of Sydney, and then wrote to scientists across Europe, Russia, North Africa, and the Middle East, asking them to send ticks for him to screen. Sure enough, he found his bugs, nestled into the ovaries of 100% of female ticks.
Soon, Lo and his colleagues began looking for a name for their new genus, which proved easier said than done. The morphology of the organism didn't present any immediate clues, and there weren't any eminent tick bacterium researchers in whose honor it could be named.
So Lo started surfing the Web, looking for ideas and finding nothing until one link took him to a page on the Wikipedia Web site describing midichlorians. He discovered that George Lucas had invented these creatures while dreaming up his Star Wars movies. The mysterious intracellular organisms apparently reside within the cells of almost all living things and communicate with the Force.
"I quite liked the earlier Star Wars movies, but I'd never heard of these midichlorians before," Lo explains. Although he's not what you'd call a Star Wars fanatic, Lo began thinking perhaps he should name his real-life organism after the imaginary ones. After all, he says, "Art is often imitating science, but it doesn't often go the other way."
In May of this year, Lo and his colleagues submitted a paper to the International Journal of Systematic and Evolutionary Microbiology suggesting that their new species be called Midichloria mitochondrii. They crossed their fingers and waited for the publishing process to take its course.
Meanwhile, one of Lo's coauthors started to get a little nervous. Weren't midichlorians the intellectual property of George Lucas? Might he sue? While the paper was out for review, Lo wrote to Lucas and sought his permission. "I was really praying he wouldn't say no," Lo says. Lucas' assistant wrote back graciously to say that George was fine with the whole thing, and on June 20, the journal accepted the paper. "One reviewer was very negative about the name, but fortunately the editor was fairly open-minded," Lo says.
The journal published the paper early last month. It turns out that Lo and his colleagues had submitted their suggestion just before the well-known French rickettsia expert, Didier Raoult, had proposed the name Nicolleia massiliensis. "As far as we know it's the first species to be formally named after anything in the entertainment industry," Lo says. "There's plenty of science in Star Wars but not enough Star Wars in science as far as I'm concerned."