Evidence for Metabolic Provisioning by a Common Invertebrate Endosymbiont, Wolbachia pipientis, during Periods of Nutritional Stress

Abstract

Wolbachia are ubiquitous inherited endosymbionts of invertebrates that invade host populations by modifying host reproductive systems. However, some strains lack the ability to impose reproductive modification and yet are still capable of successfully invading host populations. To explain this paradox, theory predicts that such strains should provide a fitness benefit, but to date none has been detected. Recently completed genome sequences of different Wolbachia strains show that these bacteria may have the genetic machinery to influence iron utilization of hosts. Here we show that Wolbachia infection can confer a positive fecundity benefit for Drosophila melanogaster reared on iron-restricted or -overloaded diets. Furthermore, iron levels measured from field-collected flies indicated that nutritional conditions in the field were overall comparable to those of flies reared in the laboratory on restricted diets. These data suggest that Wolbachia may play a previously unrecognized role as nutritional mutualists in insects.

Dynamics of the “Popcorn” Wolbachia Infection in Outbred Aedes aegypti Informs Prospects for Mosquito Vector Control

“…The faster development time is likely to increase fitness (and overall rate of population growth) because it allows larvae to complete development before a container dries out. This positive effect may reflect a nutritional mutualism between Wolbachia and the host, which has been demonstrated for iron metabolism in D. melanogaster (Brownlie et al 2009). Positive effects have also been reported in closely related naturally Wolbachia-infected Ae.…”

Effects of dietary folic acid level and symbiotic folate production on fitness and development in the fruit flyDrosophilamelanogaster

“…However, previous studies indicate fruit flies may also use nutrients from microbial symbionts. Fruit flies infected with the parasitic endosymbiont Wolbachia have better reproductive output than uninfected peers when reared on diets with abnormal levels of dietary iron, 24 although flies here likely were free of Wolbachia. The melon fly Dacus cucurbitae, which also feeds on fruit, only requires dietary folic acid when it is fed antibiotics.…”

Analysis of gene expression from theWolbachiagenome of a filarial nematode supports both metabolic and defensive roles within the symbiosis

“…Despite these considerations, several lines of evidence indicate a key role for Wolbachia in the maintenance of iron homeostasis (as opposed to simply provisioning). In D. melanogaster, wMel was shown to confer a fecundity benefit on flies reared on both ecologically relevant, iron-restricted diets and on artificial, iron-overloaded diets (Brownlie et al 2009). Moreover, in D. simulans reared under high-iron conditions, flies infected with wRi absorbed more iron than did uninfected flies, yet the up-regulation of host ferritin was lower than that observed in uninfected flies (Kremer et al 2009).…”