Microbiome in the Drosophila gut

The

The particular species of the host fly has a central influence on the composition and quality of the gut microbiota, even if flies are raised under similar conditions.[5] Nevertheless, the host's diet and nutritional environment also shape the exact composition of the microbiota. For instance the exact pH of the food can kill certain bacterial species.^[3] In general, the type of food used by the fly affects the microbiota composition.^[6] Mushroom feeder species like Drosophila falleni and Microdrosophila harbour many Lactobacillales and generally maintain high bacterial diversity in their guts. The microbiota of flower feeders such as Drosophila elegans and Drosophila flavohirta shows higher abundance of Enterobacteriaceae and to a lesser extent of acido-philic bacteria (such as Acetobacteraceae and Lactobacillaceae) if compared to fruit-eating species such as Drosophila hydei, Drosophila immigrans, Drosophila sulfurigaster, Drosophila melanogaster, Drosophila sechellia or Drosophila takahashii.^[3] The microbial load and bacterial composition also vary with the age of the host fly.^[3]

Microbiota transmission and establishment

Feeding is a key determinant of the microbiota composition. Not only the diet influences presence and abundance of the bacteria inside the gut, but the bacteria also need to be taken up continuously from the environment to prevail as members of the intestinal flora.^[7] Feeding on feces seems to play a central role for establishment of the Drosophila microbiota, as it allows the flies to recycle the bacteria within a fly population at a particular time point and also across generations. Flies seed the embryonic eggshell with feces. Upon hatching, young larvae eat their eggshells and thereby pick up the bacteria. The microbiota, which subsequently establishes itself inside the gut of the developing larvae, is similar to that of the larvae's mothers.^[8] This may further be promoted by the particular life history of the flies. Young adult flies, which harbor fewer bacteria than old flies, proliferate in an environment shaped by the feces of the preceding fly generation, thus allowing them to take up additional bacteria.^[8]

Gut compartmentalization

In the

Drosophila microbiota have been implicated in mating success by influencing assortative mating; a phenomenon detected in some studies of Drosophila,[14] but not others.^[15]

Effects on longevity

The microbiota seem to affect the lifespan of Drosophila melanogaster. To date, the mechanisms of this effect remain elusive.
Fruit flies raised under

Almost all current approaches for the characterization of Drosophila microbiota rely on destructive approaches, that is flies are killed, their gut is extracted and from these the bacteria are isolated and/or analyzed. For an assessment of microbiota dynamics across the lifespan of an individual fly or across development of a fly population, a non-destructive approach would be favorable. Such an approach was recently developed, focusing on the microbial characterization of fly feces. Fly feces are indeed informative on composition of the gut microbiota, since the diversity of gut bacteria, feces bacteria and bacteria of whole fly of Drosophila melanogaster are all strongly correlated. This new approach could be used to demonstrate the known influence of diets.[20]

References