Contrasted effects of suppressing live yeast from food on longevity, aging and resistance to several stresses in Drosophila melanogaster

It is often accepted that dietary restriction (DR) increases longevity in Drosophila melanogaster, but this is still a controversial issue. In the present study, adult flies were fed on a rich nutritious medium to which live yeast, a source of proteins, was added or not. Suppressing live yeast did not always increased longevity of virgin flies, but increased it in mated flies. It also decreased fecundity, delayed behavioral aging and increased resistance to heat of young females only. However, flies without live yeast suffered from a reduced resistance to cold, starvation and infection. This study thus reports some positive effects of suppressing live yeast on longevity, contrarily to previous studies of the same laboratory using other DR methods, but also shows that the absence of live yeast increases frailty. The effects of live yeast in flies are thus contrasted, and it is probable that flies without a high amount of proteins in the diet would not survive for a long time in the wild, due to their inability to resist stress and their low fecundity.