Delayed larval development in Anopheles mosquitoes deprived of Asaiabacterial symbionts

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.

Asaiaaccelerates larval development ofAnopheles gambiae

“…This would render the need for repeated introductions unnecessary, which would reduce the cost substantially for such a strategy. As recently shown in another study, 20 when mosquitoes are deprived of Asaia symbionts they experience a delay in larval development. This, combined with our observations that there is an increase in the developmental rate when additional bacteria are introduced into the organism, leads us to the conclusion that Asaia plays a yet undetermined crucial role during the larval stages.…”

“…Therefore, these bacteria can be considered excellent candidates for use as agents of paratransgenesis in a vector-centered fight against malaria. Taken together with the observation that Asaia is reduced using rifampicin treatment, 20 we tend to conclude that the bacteria are needed to maintain the developmental rate of the larvae. The molecular nature of the developmental accelerator, though, remains to be identified.…”

Origin and Effect of Alpha 2.2 Acetobacteraceae in Honey Bee Larvae and Description of Parasaccharibacter apium gen. nov., sp. nov

“…Instead, it appears that some of the major microbial players in nongut hive niches are those able to tolerate the sugary and acidic environments of the crop, bee bread, larval guts, and royal jelly, such as Acetobacteraceae Alpha 2.2 (Alpha 2.2) (10,12). Acetobacteraceae are symbionts of a wide variety of insects, providing nutrition to insects on limited sugar-rich diets (13), benefiting development and the formation of tissues (14,15), and modulating immunity (16). They are commonly found in the insect gut (13) but have also been isolated from salivary glands and reproductive tissues (14).…”

“…Acetobacteraceae are symbionts of a wide variety of insects, providing nutrition to insects on limited sugar-rich diets (13), benefiting development and the formation of tissues (14,15), and modulating immunity (16). They are commonly found in the insect gut (13) but have also been isolated from salivary glands and reproductive tissues (14). Acetobacteraceae Alpha 2.2 bacteria are closely related to Saccharibacter sp.…”

Contaminants of emerging concern affect Trichoplusia ni growth and development on artificial diets and a key host plant

“…Many herbivores can be exposed to these contaminants after the CECs enter surface waters, soil, and plants from wastewater reuse and unintended discharge. To investigate the function of the gut microbes in insects, several studies have used antibiotics applied at high doses (47,48). There is also no information regarding effects of CECs when translocated through plants to terrestrial insects.…”