Pantoea agglomerans

Researchers report they have found a way to kill malaria in mosquitoes by genetically modifying a bacterium commonly found in the insect’s mid-gut, according to a new study.

The bacterium, called Pantoea agglomerans, can be modified to secrete proteins that are toxic to the malaria parasite, but are not harmful to humans or the mosquito itself.  In fact, the bacterium is so specific to targeting malaria that it does not even affect other bacteria in the mosquito’s gut, according to the researchers from Johns Hopkins Malaria Research Institute, who conducted the study.
The bacterium is genetically engineered to attack malaria in multiple ways.

“There are not one, but several anti-malaria compounds the bacterium secretes,” explained Dr. Marcelo Jacobs-Lorena, senior author of the study and a professor at the Johns Hopkins Bloomberg School of Public Health.  “Each acts by a different mechanism and makes it much more difficult for the parasite to develop a resistance to it.”
One of the compounds secreted by the bacteria, for example, inserts itself into the membrane of malaria parasite, essentially poking holes in the parasite’s protective outer layer and causing it to ‘leak out’ and die.  Another one of the compounds binds itself to a crucial protein the parasite needs to survive, thus blocking the parasite from the taking advantage of the protein.
According to the researchers, the bacterium successfully inhibited the development of the deadliest human malaria parasite, known as Plasmodium falciparum, and the rodent malaria parasite, Plasmodium berghei, by up to 98 percent in a small preliminary study. The bacterium reduced the prevalence of malaria among the mosquitoes by up to 84 percent.
Past approaches to fighting malaria in mosquitoes focused around genetically modifying the insects themselves to resist malaria.  However, scientists found – while successful in the lab – it was much more difficult to spread the genetic changes in nature.
“We changed the strategy, taking advantage of the fact that mosquitoes, like humans, carry big population of bacteria in their guts,” Jacobs-Lorena said.  “We took one of bacteria and engineered it to produce anti-malaria proteins.  We re-introduced it back into the mosquitoes and found it works quite well.”
The reason this approach cannot be taken in humans, he added, is that while mosquitoes carry malaria in their guts, malaria nearly exclusively spreads through the bloodstream to the liver in humans – completely bypassing the gut.