The parasite that causes malaria in humans, Plasmodium falciparum, researchers at the Johns Hopkins Bloomberg School of Public Health have found, can be killed by a bacterium in mosquitoes itself.
The Enterobacter bacterium is part of the naturally occurring microbial flora of the mosquito's gut and kills the parasite by producing reactive oxygen species (or free radical molecules).
"We've previously shown that the mosquito's midgut bacteria can activate its immune system and thereby indirectly limit the development of the malaria parasite," said George Dimopoulos, senior author of the study.
"In this study we show that certain bacteria can directly block the malaria parasite's development through the production of free radicals that are detrimental to Plasmodium in the mosquito gut.
"We are particularly excited about this discovery because it may explain why mosquitoes of the same species and strain sometimes differ in their resistance to the parasite, and we may also use this knowledge to develop novel methods to stop the spread of malaria," said Dimopoulos..
For the study, the researchers isolated the Enterobacter bacterium from the midgut of Anopheles mosquitoes collected near the Johns Hopkins Malaria Research Institute at Macha, which is located in southern Zambia.
About 25 percent of the mosquitoes collected contained the specific bacteria strain.
Laboratory studies showed the bacterium inhibited the growth of Plasmodium up to 99 percent, both in the mosquito gut and in a test tube culture of the human malaria parasite.
The study has been published in the May 13 edition of Science.