Researchers have a new clue to the collapse of honey bee colonies across the U.S. — damage to the bees' internal "factories" that produce proteins.
Theories about the cause of bee colony collapse have included viruses, mites, pesticides and fungi.
The new study of sick bees disclosed fragments of ribosomal RNA in their gut, an indication of damage to the ribosomes, which make proteins necessary for life, according to a study in Tuesday's issue of Proceedings of the National Academy of Sciences.
RNA, which is made from DNA, is central to protein production.
The sick bees suffered an unusually high number of infections with viruses that attack the ribosome, the researchers from the University of Illinois at Urbana-Champaign and the U.S. Department of Agriculture reported.
"If your ribosome is compromised, then you can't respond to pesticides, you can't respond to fungal infections or bacteria or inadequate nutrition because the ribosome is central to the survival of any organism. You need proteins to survive," May R. Berenbaum, head of the department of entomology at Illinois, said in a statement.
The researchers said the varroa mite, which was accidentally introduced to the U.S. in 1986, is a carrier of picorna-like viruses that damage the ribosomes.
The mite may act as a tipping factor leading to ribosome breakdown, the researchers said.
The study was funded by the Department of Agriculture.