Invasive brown widow spiders have been found to host new chlamydia-related bacteria

Invasive brown widow spiders on three continents were highly infected with a single strain of Rhabdochlamydia, a bacterium that is related to major human and animal pathogens, including chlamydia. However, bites from these spiders do not infect humans with chlamydia.

So far, rhabdoclamydia have only been found in a few organisms—a tick, an isopod, a cockroach, and one other spider—and even then they were a rare occurrence in all of those organisms.

Dr. Monica Mowery and colleagues at Ben-Gurion University of the Negev compared microbial communities in populations of brown widow spiders collected in South Africa (the spider’s likely native range) and invasive populations in Israel and the United States. The most prevalent bacteria, Rhabdochlamydia, was found in 86% of the spiders examined. It was also found in the eggs of female spiders, suggesting that mother spiders pass the bacteria on to their offspring.

“Our results suggest that this dominant, widespread chlamydial bacterium has an important role in the invasive brown widow spider,” explained Dr. Mowery, an assistant professor at the City University of New York and a former postdoctoral researcher at BGU.

A study was recently published in Scientific reports.

Characterization of potentially important and widespread bacterial symbionts is a step toward understanding their importance for ecological interactions and responses to rapid environmental change. The high prevalence of Rhabdochlamydia in all spider populations tested suggests that it may have an important functional role and could contribute to spider invasion success.

The brown widow spider, Latrodectus geometricus, is an urban invasive species that outcompetes native spider species found in warm climates around the world. These spiders have neurotoxic venom and can be dangerous for small children and the elderly.

Microbial associates can influence the spread of an invading species and success in a new environment and can shift or be lost during the invasion process. South African brown widow spiders had more distinct strains of bacteria overall compared to more recent additions in Israel, where brown widows were first found in Tel Aviv in 1980, and in the United States, where the spiders spread from southern Florida in 2000. This higher microbial diversity supports the idea that the invasive brown widow spider originated in southern Africa.

Other researchers included Prof. Yael Lubin and Prof. Michal Segoli from Ben-Gurion University of the Negev, prof. Jennifer White, Ph.D. Eric Chapman and Laura Rosenwald of the University of Kentucky, Thembile Khoza of the South African National Biodiversity Institute, and Robin Lyle of the Agricultural Research Council, South Africa.