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Careful Look Into Drosophila Sequences Uncovers Genomes of Several Endosymbionts

NEW YORK, Feb. 28 (GenomeWeb News) - Finishing sequencing the genomes of seven species of Drosophila last year, a team of researchers at the University of California, Berkeley, had inadvertently sequenced the genes of several bacteria that secretly live in fruit fly embryos.

These bacteria, which belong to the Wolbachia genus, reside in the Drosophila gene database, where they lived quietly, and, until now, unnoticed, according to Michael Eisen, a UC Berkeley assistant professor of molecular and cell biology and a faculty scientist at Lawrence Berkeley National Laboratory.


"The sequencers who did the Drosophila species didn't even notice this because this is just a very small fraction of the total sequence and it was sort of tossed into the garbage," Eisen said in a statement released by US Berkeley. "In every genome there is always stuff that doesn't make sense, and people weren't looking for it. We thought this was interesting as much for the novelty of the way the bacterial genomes were sequenced than what we learned about the bacteria themselves."

After his discovery -- and largely because he's a Drosophila geneticist and "not an expert on bacteria" -- Eisen sought the help of The Institute for Genomic Research, and soon hooked up with Steven Salzberg, TIGR's director of bioinformatics.


"The discovery of these three new genomes demonstrates how powerful the public release of raw sequencing data can be," the authors wrote in their study describing the discovery, which appears in the current issue of Genome Biology, published this week. The authors have deposited their data in Genbank.


According to Eisen, these bacterial species live inside the fruit fly genome database because of the way the fly was sequenced: Researchers ground up embryos and extracted their DNA, "meaning that any endosymbionts ... would have had their DNA intermixed with fly DNA before sequencing," according to the statement.

"There is a lot of unexplored stuff out there in the genome databases -- it's certainly not out of the question that other genomes have these lurking endosymbionts," Eisen said.

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