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News Article

Gut bacteria alter food choice in Drosophila flies


Two species suppress choice of protein rich food when flies are on deficient diets

Neuroscientists have discovered that gut bacteria "speak" with the brain to control food choices in animals. They identified two species of gut bacteria that have a radical impact on dietary decisions in fruit flies, a commonly used animal model. Gut bacteria seem to help drosphila fruit flies deal with deficiencies in certain nutrients, allowing them to continue to reproduce, as well as influencing their appetite for those nutrients.

The microbiome, the community of bacteria that resides in an animal's gut, including human beings, is increasingly been shown to impact health and to manipulate various biological pathways such as those for immunity and appetite. For instance, diseases like obesity have been associated with the composition of the diet and the microbiome. The relationships are complex and the team from the Champalimaud Centre for the Unknown (CCU), in Lisbon, Portugal, in collaboration with a colleague from Monash University, Australia have simplified the situation by studying fruit flies that have defined bacterial populations of gut microbes and defined diets.

The new study published in PLoS Biology, showed that the impact of the flies’ gut bacteria is so profound that, when the flies were fed a defined diet lacking certain essential nutrients, these bacteria stopped them from developing an appetite for those nutrients - and also protected them from the consequences of their absence. The bacteria literally reprogrammed the body's nutritional needs, to the point that they even safeguarded the flies' fertility, which would otherwise have been abolished by the low quality of the diet.

The team initially studied flies with low levels of gut bacteria feeding on the complete defined diet and then they removed single essential amino acids from the flies’ diets and compared their choice of protein rich foods with that of flies on the complete defined diet. They found that removal of any single essential amino acid from the defined diet in flies with low levels of gut bacteria was sufficient to strongly increase the flies' choice of a protein-rich food.

The scientists then used flies that had defined species of bacteria in their guts and tested their food choices while they were on the essential amino acid deficient diets. Surprisingly, they found that flies with two bacterial species in their guts (Acetobacter pomorum and Lactobacilli) did not choose protein rich food more often when on the deficient diets, and were able to continue reproducing in spite of their deficient diet, even when they were deprived of all of the essential amino acids tested at once.

"With the right microbiome, fruit flies are able to face these unfavorable nutritional situations", says Zita Santos, one of the study authors.

How could the bacteria act on the brain to alter appetite? "Our first hypothesis was that these bacteria might be providing the flies with the missing essential amino acids", Santos replies. However that doesn’t seem to be the whole story and an unkown mechanism seems to be at work.

It’s a big step from flies to man but they are models for all kinds of processes across the animal kingdom. It will be interesting to see if this effect can be seen in other animal models.

Commensal bacteria and essential amino acids control food choice behavior and reproduction. Leitão-Gonçalves R, Carvalho-Santos Z, Francisco AP, Fioreze GT, Anjos M, Baltazar C, et al. (2017) PLoS Biology15(4): e2000862. https://doi.org/10.1371/journal.pbio.2000862

 

Article details

  • Author(s)
  • I. Hoskins
  • Date
  • 26 April 2017
  • Subject(s)
  • Nutrition & health