Research Focuses on Black Widows
By Edwin L. Aguirre
Biology Asst. Prof. Jessica Garb loves spiders. She has been studying the eight-legged creatures for years.
“As an undergraduate at Cornell University, I was lucky enough to take an entire class on spider biology,” says Garb. “It was one of my favorite courses and I was hooked. I had always been interested in all sorts of biology before then, but I had no idea how interesting and diverse spiders were.”
Garb’s current research involves applying new technologies to determine how the venom of black widow spiders became so powerful.
“I have a lot of expertise on spiders but none on snakes and scorpions,” she says. “Spider venom is more interesting to me because relative to snake and scorpion venom, it is not as well studied.”
Garb uses advanced DNA sequencing techniques to characterize all the genes from the black widow spider that encode venom proteins.
“This work will be done with multiple, closely related spider species, giving us an unprecedented understanding of venom evolution and how the black widow spider’s venom became so potent,” she says. “Spider venom has never before been studied at such a large genomic scale, and very little is known about the molecules that make up black widow venom and their evolution.”
The U.S. National Institutes of Health recognized the importance of her study and recently awarded her with a grant totaling $294,656 over three years.
Painful but Rarely Fatal
Of the 40,000 species of spiders that have been identified so far, the black widow (whose scientific name is Latrodectus mactans) is arguably the best known. They are found throughout North America, but are most common in the warm southern and western parts of the United States. They normally hide in largely undisturbed areas such as garages, attics, basements, barns, woodpiles, eaves, fences and outdoor furniture.
Adult female black widows, which have unusually large venom glands, are usually distinguished by their shiny black body and the red “hourglass” marking on their bellies. When threatened, they will use their fangs to inject a powerful neurotoxin into the victim’s flesh, which produces pain at the bite area and then spreads to the chest, abdomen or the entire body.
“Bites from female black widow spiders are usually not lethal for healthy adult humans — they are just extremely painful,” says Garb, adding that there is a very effective antivenom for the black widows’ neurotoxin.
“One problem, however, is that the antivenom sometimes elicits strong allergic reactions in people who receive it. The work I am doing may help create more effective antivenoms that can be tailored to minimize negative side effects,” she says.
Some toxin molecules in animal venoms actually can have beneficial effects in humans. For example, biomedical researchers have modified these toxins to block specific nerve channels or prevent blood from clotting.
“For this reason, some venom toxins have been developed into pharmaceutical drugs such as Ziconotide, which is extracted from cone snail venom and is used to treat severe and chronic pain, as well as chlorotoxin, from Israeli yellow scorpion venom, which is used to treat brain cancer,” says Garb. “Black widow venom may also contain a variety of molecules with potential as drug leads — we are taking the first step in finding out what the molecular components of this venom are.”
Nature’s Wonder Fiber
In addition to spider venom toxins, Garb’s other major area of research is on the molecular biology and evolution of spider silk.
“Spider silk is famous for its exceptional mechanical properties, surpassing steel and Kevlar in toughness and energy absorption,” she says.
What fascinates her about the fiber is that it is so varied — some spiders make up to seven different kinds of silk for specialized functions, such as spinning webs, making egg cases and wrapping their prey.
“Each of these silk types is composed of different proteins, which determine how strong or stretchy the fiber is,” she says. “I have been working to characterize the genes that make up these silk proteins and to understand how the various silk types have evolved within and among spider species. Engineers can use this genetic information to make artificial spider silk for medical and material applications.”