Researchers have sequenced the genome of the common bedbug for the first time, providing unprecedented insight into one of the world’s most troublesome urban pests.
The highly ambitious project, which involved 36 different institutions and over 80 scientists, used samples from both preserved and living bedbugs, known more technically as Cimex lectularius, to sequence both DNA and RNA. The oldest samples used have been held by the American Museum of Natural History (AMNH) since their acquisition in 1973.
“It’s not enough to just sequence a genome, because by itself it does not tell the full story,” said Mark Siddall, study corresponding author and curator in AMNH’s Division of Invertebrate Zoology and Sackler Institute for Comparative Genomics.
“In addition to the DNA, you want to get the RNA, or the expressed genes, and you want that not just from a single bedbug, but from both males and females at each part of the life cycle. Then you can really start asking questions about how certain genes relate to blood-feeding, insecticide resistance and other vital functions.”
Bedbugs have soared in numbers in recent years. In Australia alone bedbug infestations have risen 4,500% since 1999.
“Bedbugs all but vanished from human lives in the 1940s because of the widespread use of DDT, but, unfortunately, overuse contributed to resistance issues quite soon after that in bedbugs and other insect pests,” said Louis Sorkin, study co-author and senior scientific assistant in AMNH’s Division of Invertebrate Zoology. “Today, a very high percentage of bedbugs have genetic mutations that make them resistant to the insecticides that were commonly used to battle these urban pests.”
“Nobody was ready for this,” added Michael Scharf, the O Wayne Rollins / Orkin Chair in Molecular Physiology and Entomology at Perdue University. “It’s reached almost a crisis condition. All big cities in the US are experiencing problems. Our culture had forgotten about bedbugs, and two generations of entomologists haven’t had to deal with them.”
The research has produced numerous insights into bedbugs that may aid their extermination, but one finding in particular stands out: the presence of genes from the bacteria Wolbachia in the bedbug genome. The result of a process known as lateral gene transfer, the gene appears to only function in male bedbugs.
“Genomic sequences from Wolbachia are present in the bedbug genome,” said Coby Schal, project co-leader and North Carolina State University Blanton J Whitmire Distinguished Professor of Entomology. “We don’t know if the bacterium is co-opting the bedbug or if the bedbug is co-opting the bacterium. Very few of these bacterial genes are functional and we don’t know what proteins they are producing. But it would be fascinating if bacterial genes that are useful to the bedbug, such as those involved in B vitamin metabolism, were incorporated into the bedbug genome.”
“Because the inserted genes create unique genetic profiles in bedbugs, they have the potential of becoming effective targets for pest control,” added Jack Werren, professor of biology at the University of Rochester.
By using samples from across the bedbugs’ lifecycle, the researchers were also able to identify specific stages where they would be most resistant to insecticide.
In particular, certain genes that were only expressed after the bedbugs drank blood for the first time were found to be linked to insecticide resistance, as they provided, for example, improved detoxification or thicker skin – known as chitin.
As a result, future insecticides may be developed to target bedbugs at the first nymph stage, before they have had a chance to sample human blood.