Combined effects of suppressing live yeast and of a cold pretreatment on longevity, aging and resistance to several stresses in Drosophila melanogaster.

A cold pretreatment has various positive effects on aging, longevity, and resistance to some stresses in Drosophila melanogaster flies. Removing live yeast from food has either favorable or deleterious effects on these traits. This study combined a cold pretreatment and removal of live yeast in the same flies, in order to know whether higher favorable effects would be observed with this combination than with each treatment alone. Each treatment had positive effects on climbing activity and their combination had additive effects, thus giving the highest climbing scores in flies subjected to the two treatments and the lowest ones in flies with live yeast and no cold pretreatment. Therefore, combining the two treatments had favorable effects if each of them had favorable effects. When removing live yeast had very deleterious effects, as on resistance to cold, a cold pretreatment was unable to reverse these effects, which was not unexpected. Finally, when removal had no effect or not a tragic negative effect, as on resistance to infection or to heat, a cold pretreatment was neutral or slightly compensated the negative effects of live yeast removal. These results lead to the conclusion that next studies using a combination of two mild stresses having beneficial effects on aging and longevity could bring more positive effects than each mild stress alone.