Human body louse genome sequenced
An international team of scientists has successfully sequenced the genome of that most majestic of creatures, the body louse. Like head lice, body lice attach themselves to human hosts and live off their blood. Unlike head lice, however, body lice can spread bacterial diseases. By understanding more about the creature, the team hopes to develop better methods of controlling it.
Coordinated by University of Illinois entomology professor Barry Pittendrig, the scientists discovered a very limited genome. Body lice already have the smallest known genome of any insect, but because they’re designed to do almost nothing except live in people's clothes and drink their blood... well, let’s just say they haven’t exactly kept their options open. Besides having very few genes for light-sensing protein receptors, for instance, they also have fewer taste and odor receptors than other insects.
It also has the smallest number of detoxification enzymes observed in any insect, which could make it an ideal candidate for testing resistance to pesticides.
The body louse is dependent on its human host for survival, but is just as reliant on a microbe that lives within it - the bacterium Candidatus Riesia pediculicola. In the Riesa genome, the team found genes for the production of the nutrient pantothenate (Vitamin B5), which the louse requires and cannot make on its own. Because it has evolved in such an unchanging environment, Riesa has no resistance to antibiotics. If this bacterium could be controlled, then the body louse population would follow.
The Riesa genome is quite small compared to its closest relatives. The same can be said of the genomes of several other bacteria found on body lice, which are known to spread diseases including typhus, relapsing fever, and trench fever. This fact, according to the research team, “will make the body louse a useful tool for understanding the co-evolution of disease-carrying parasites and their bacterial co-conspirators.”
The research was recently published in Proceedings of the National Academy of Sciences.