Abstract
BackgroundIn recent years, acetic acid bacteria have been shown to be frequently associated with insects, but knowledge on their biological role in the arthropod host is limited. The discovery that acetic acid bacteria of the genus Asaia are a main component of the microbiota of Anopheles stephensi makes this mosquito a useful model for studies on this novel group of symbionts. Here we present experimental results that provide a first evidence for a beneficial role of Asaia in An. stephensi.ResultsLarvae of An. stephensi at different stages were treated with rifampicin, an antibiotic effective on wild-type Asaia spp., and the effects on the larval development were evaluated. Larvae treated with the antibiotic showed a delay in the development and an asynchrony in the appearance of later instars. In larvae treated with rifampicin, but supplemented with a rifampicin-resistant mutant strain of Asaia, larval development was comparable to that of control larvae not exposed to the antibiotic. Analysis of the bacterial diversity of the three mosquito populations confirmed that the level of Asaia was strongly decreased in the antibiotic-treated larvae, since the symbiont was not detectable by PCR-DGGE (denaturing gradient gel electrophoresis), while Asaia was consistently found in insects supplemented with rifampicin plus the antibiotic-resistant mutant in the diet, and in those not exposed to the antibiotic.ConclusionsThe results here reported indicate that Asaia symbionts play a beneficial role in the normal development of An. stephensi larvae.
Highlights
In recent years, acetic acid bacteria have been shown to be frequently associated with insects, but knowledge on their biological role in the arthropod host is limited
Acetic acid bacteria (AAB) of the genus Asaia have been shown to be stably associated with larvae and adults of the malaria mosquito vectors An. stephensi, An. maculipennis and An. gambiae [6,7] where they form a main component of the mosquito-associated microbiota
Asaia is important for larval development The effects of rifampicin treatment on the An. stephensi larval development are reported in Figure 1 and 2
Summary
Acetic acid bacteria have been shown to be frequently associated with insects, but knowledge on their biological role in the arthropod host is limited. The discovery that acetic acid bacteria of the genus Asaia are a main component of the microbiota of Anopheles stephensi makes this mosquito a useful model for studies on this novel group of symbionts. AABs have been described as emerging symbionts of insects being found associated especially with those with a sugar-feeding habit [4,5]. AAB of the genus Asaia have been shown to be stably associated with larvae and adults of the malaria mosquito vectors An. stephensi, An. maculipennis and An. gambiae [6,7] where they form a main component of the mosquito-associated microbiota. Asaia is a versatile symbiont being capable of cross-colonizing insects from phylogenetically distant taxa [8] and of vertical, venereal and paternal transmission [9]
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