Bacteria participate in mosquito defense against oxidative stress

Anautogenous female mosquitoes take a blood meal for egg production. Blood digestion results in heme associated oxidative stress, which is detrimental to various life traits, such as fecundity and longevity. As an adaptation, mosquitoes have evolved certain antioxidant mechanisms to cope with the stress. However, little is known about the contribution of the gut bacteria on mosquito phenotypes. Paraquat is an herbicide known to causes extensive damage to mitochondria through the production of free radicals and oxidative stress. In this study we feed mosquitoes with paraquat and examined the effect of paraquat on mosquito fecundity and mortality. Compared to normal sugar control, paraquat feeding increased the mortality and decreased the fecundity. In addition, the blood meal and paraquat shifted the structure of bacterial community in the gut. For example, the relative abundance of Elizabethkingia and Enterobacter increased in the paraquat fed gut, while the abundance of Pseudomonas reduced in response to paraquat feeding. In vitro culture in the presence of paraquat, Elizabethkingia and Enterobacter tolerate mcuh higher paraquat concentration than Pseudomonas. The data suggest oxidative stress tolerant bacteria may be involved in the redox homeostasis in mosquito gut ecosystem. Comparison among the three strains on the reducing power such as the ratios of NADPH/NADP and GSH/GSSG is underway.