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Figure 4: Attempt to recover function in P3G5-containing fies using acetic acid
In addition to its involvement in IIS activation, PQQ-ADH is an important enzyme in the ethanol oxidative respiratory chain. This biological process produces acetic acid, and the authors observed that all the bacterial mutant strains they examined in Figure 1, including P3G5, produced abnormally low levels of acetic acid. So, to test the hypothesis that the metabolic and developmental deficits of flies containing P3G5 bacteria were due to low acetic acid levels, they supplemented their diets with acetic acid.
Image from Shin et al., 2011
Panel A: As in Figure 3A, shows localization of dFOXO in flies containing WT and P3G5 bacteria, and in flies containing P3G5 bacteria and receiving acetic acid supplements. Although dFOXO was not retained in the cytoplasm of P3G5 bacteria-containing flies, it was retained in P3G5 bacteria containing flies whose diets were supplemented with acetic acid.
Panel B: Time to puparium formation (y-axis) was compared in flies containing WT and P3G5 bacteria, in flies containing P3G5 bacteria and receiving acetic acid supplements, and in germ-free flies receiving acetic acid supplements (x-axis). Flies containing P3G5 bacteria showed delayed devlopment, although they displayed normal development rates if their diets were supplemented with acetic acid. Acetic acid supplements were not sufficient for survival of germ-free flies. Images show larvae at 120 hours of growth.
Panel C: Adult (five-day old) body size of flies (y-axis) is compared in flies containing WT and P3G5 bacteria, and in flies containing P3G5 bacteria and receiving acetic acid supplements (x-axis). Although P3G5 bacteria-containing flies were significantly smaller than WT bacteria-containing flies, dietary acetic acid supplements allowed P3G5 bacteria-containing flies to reach normal size.
Panel D: Wing size, cell size, and cell number (y-axis) of adult (five-day old) flies is compared in flies containing WT and P3G5 bacteria, and in flies containing P3G5 bacteria and receiving acetic acid supplements (x-axis). All three dependent variables were reduced in P3G5 bacteria-containing flies, but P3G5 bacteria-containing flies reached normal wing size, cell size, and cell number with dietary acetic acid supplements.
Panel E: Blood sugar and lipid levels (y-axis) are compared in flies containing WT and P3G5 bacteria, and in flies containing P3G5 bacteria and receiving acetic acid supplements (y-axis). Both blood sugar and lipid levels were elevated in P3G5 mutant bacteria-containing flies, but mutant bacteria-containing flies demonstrated normal blood sugar and lipid levels with dietary supplementation of acetic acid.
Reference:
Shin, C. S., Kim, S., You, H., Kim, B., Kim, A. C., Lee, K., Yoon, J., Ryu, J., Lee, W. 2011. Drosophila Microbiome Modulates Host Development and Metabolic Homeostasis via Insulin Signaling. Science. 334: 670-674.
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