Study clarifies role of bacteria in pandemic diseases

Jul 04, 2013

(Phys.org) —Wolbachia are intracellular bacteria that infect invertebrates at pandemic levels, including insects that cause such devastating diseases as Dengue fever, West Nile virus, and malaria. While Wolbachia-based technologies are emerging as promising tools for the control of the insect vectors of these deadly diseases, the processes underlying Wolbachia's successful propagation within and across species remain elusive.

A new study by CAS researchers sheds light on some of these processes by providing evidence that Wolbachia target the ovarian stem cell niches of its hosts—a strategy previously overlooked to explain how Wolbachia thrive in nature. The study, "Evolutionarily conserved Wolbachia-encoded factors control pattern of stem-cell niche tropism in Drosophila and favor infection," has been published in the current issue of PNAS Early Edition, available online here. Michelle Toomey, a CAS Biology PhD student, and Kanchana Panaram, a former in the Frydman Lab at the Department of Biology, are the study's co-first authors.

Although Wolbachia are mainly vertically transmitted (from the parental generation of the species to the offspring), there is also evidence of extensive horizontal transmission (from one individual to another in the same generation). The study shows that both vertical and horizontal transmission occurs through Wolbachia's preference for the region of the insect ovary that contains , known as "stem cell niches". Tropism—in which different viruses or pathogens evolve to preferentially target specific cell types within a host—for stem cell niches is pervasive in Wolbachia that infect the Drosophila (fruit fly) genus.

Using cell biological, phylogenetic, genetic, and transinfection tools, the BU team found evidence that stem-cell niche tropism is an evolutionarily conserved mechanism for Wolbachia hereditary and non-hereditary transmission, and that this tropism is a widespread occurrence across the Drosophila genus. Phylogenetic analyses also revealed selective pressures promoting strong conservation of the same pattern of niche tropism among closely related Wolbachia strains. Using hybrid crosses and transinfection experiments, the researchers demonstrated that Wolbachia-encoded factors, rather than the host genetic background, are the major determinants of different patterns of stem cell niche tropism.

"Because Wolbachia are maternally transmitted, their presence in the germ line is essential for their vertical propagation to the next generation," says Toomey.  "However, Wolbachia are often found in several somatic tissues as well, and this distribution varies among different Wolbachia–host associations."

The study indicates it is easier for Wolbachia to reach the germ line through the stem cell niches during vertical transmission and probably during horizontal transmission as well.

"Wolbachia represent the first reported case of bacteria living in a stem cell niche. The data presented in this study provide the foundation for future methodologies toward the identification of genetic pathways mediating Wolbachia's stem-cell niche tropism in hosts," says Horacio Frydman, assistant professor of biology. Understanding the basis of Wolbachia targeting of specific tissues in the host and its consequences toward bacterial transmission will provide further insight into their extremely successful propagation and help identify new Wolbachia-based vector control approaches.

Explore further: Research sheds light on what causes cells to divide

More information: www.pnas.org/cgi/content/short/1301524110

Related Stories

How Wolbachia bacteria controls vectors of deadly diseases

Oct 20, 2011

Researchers at Boston University have made discoveries that provide the foundation towards novel approaches to control insects that transmit deadly diseases such as dengue fever and malaria through their study of the Wolbachia bacter ...

Taking the sting out of insect disease

Oct 31, 2008

(PhysOrg.com) -- University of Queensland researchers have made a discovery that could open up a new front in the fight against insect-transmitted diseases.

Novel control of Dengue fever

Aug 24, 2011

The spread of Dengue fever in northern Australia may be controlled by a bacterium that infects mosquitoes that harbor the virus, Australian and U.S. researchers report Aug. 25 in two papers published in the journal Nature.

Recommended for you

Research sheds light on what causes cells to divide

Dec 24, 2014

When a rapidly-growing cell divides into two smaller cells, what triggers the split? Is it the size the growing cell eventually reaches? Or is the real trigger the time period over which the cell keeps growing ...

Locking mechanism found for 'scissors' that cut DNA

Dec 24, 2014

Researchers at Johns Hopkins have discovered what keeps an enzyme from becoming overzealous in its clipping of DNA. Since controlled clipping is required for the production of specialized immune system proteins, ...

Scrapie could breach the species barrier

Dec 24, 2014

INRA scientists have shown for the first time that the pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological ...

Extracting bioactive compounds from marine microalgae

Dec 24, 2014

Microalgae can produce high value health compounds like omega-3s , traditionally sourced from fish. With declining fish stocks, an alternative source is imperative. Published in the Pertanika Journal of Tr ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.